Can you elaborate on that?
The assumption that "physical" makes a substance of anything, is an illusion. There's no such thing. According to the rules of the simulation, birds fly due to aerodynamics, their wings designed in a way, their body, etc, it allows them to fly.
Yet in reality, all there is things existing in God's vision, which is the true nature of existence. Qualia. For example, who you are. That is not physical. But it's not some sort of ultra physical thing either. It's vision of God where you exist. Not space. Not time though you experience things in time, it's not where you exist. You exist in God's vision.
So birds are not really being held by aerodynamics etc but it's as expressed in this verse:
أَوَلَمْ يَرَوْا إِلَى الطَّيْرِ فَوْقَهُمْ صَافَّاتٍ وَيَقْبِضْنَ ۚ مَا يُمْسِكُهُنَّ إِلَّا الرَّحْمَٰنُ ۚ إِنَّهُ بِكُلِّ شَيْءٍ بَصِيرٌ | Have they not regarded the birds above them spreading and closing their wings? No one sustains them except the All-beneficent. Indeed, He watches all things. | Al-Mulk : 19
Like wise our body parts are not physical things since such things are impossible:
وَيَوْمَ يُحْشَرُ أَعْدَاءُ اللَّهِ إِلَى النَّارِ فَهُمْ يُوزَعُونَ | The day the enemies of Allah are marched out toward the Fire, while they are in check, | Fussilat : 19
حَتَّىٰ إِذَا مَا جَاءُوهَا شَهِدَ عَلَيْهِمْ سَمْعُهُمْ وَأَبْصَارُهُمْ وَجُلُودُهُمْ بِمَا كَانُوا يَعْمَلُونَ | when they come to it, their hearing, their eyes and their skins will bear witness against them concerning what they used to do. | Fussilat : 20
وَقَالُوا لِجُلُودِهِمْ لِمَ شَهِدْتُمْ عَلَيْنَا ۖ قَالُوا أَنْطَقَنَا اللَّهُ الَّذِي أَنْطَقَ كُلَّ شَيْءٍ وَهُوَ خَلَقَكُمْ أَوَّلَ مَرَّةٍ وَإِلَيْهِ تُرْجَعُونَ | They will say to their skins, ‘Why did you bear witness against us?’ They will say, ‘We were given speech by Allah, who gave speech to all things. He created you the first time, and you are being brought back to Him. | Fussilat : 21
وَمَا كُنْتُمْ تَسْتَتِرُونَ أَنْ يَشْهَدَ عَلَيْكُمْ سَمْعُكُمْ وَلَا أَبْصَارُكُمْ وَلَا جُلُودُكُمْ وَلَٰكِنْ ظَنَنْتُمْ أَنَّ اللَّهَ لَا يَعْلَمُ كَثِيرًا مِمَّا تَعْمَلُونَ | You did not use to conceal yourselves [while perpetrating sinful acts] lest your hearing, your eyes, or your skins should bear witness against you, but you thought that Allah did not know much of what you did. | Fussilat : 22
وَذَٰلِكُمْ ظَنُّكُمُ الَّذِي ظَنَنْتُمْ بِرَبِّكُمْ أَرْدَاكُمْ فَأَصْبَحْتُمْ مِنَ الْخَاسِرِينَ | That misjudgement, which you entertained about your Lord ruined you. So you became losers.’ | Fussilat : 23
The thing is about verse 41:21, is that the word is not just that everything is given speech, but speech of the rational type, of logical reasoning type. So it's not just sound or expression, it means everything is given rational speech.
Right now, we see things they appear physical, but in the spiritual world, everything glorifies God. For example, per Quran, mountains would glorify with Dawood (a):
وَلَقَدْ آتَيْنَا دَاوُودَ مِنَّا فَضْلًا ۖ يَا جِبَالُ أَوِّبِي مَعَهُ وَالطَّيْرَ ۖ وَأَلَنَّا لَهُ الْحَدِيدَ | Certainly We gave David from us grace: ‘O mountains and birds, chime in with him!’ And We made iron soft for him, | Saba : 10
And said:
سَبَّحَ لِلَّهِ مَا فِي السَّمَاوَاتِ وَالْأَرْضِ ۖ وَهُوَ الْعَزِيزُ الْحَكِيمُ | Whatever there is in the heavens and [whatever there is on] the earth glorifies Allah and He is the All-mighty, the All-wise. | Al-Hadid : 1
And said:
تُسَبِّحُ لَهُ السَّمَاوَاتُ السَّبْعُ وَالْأَرْضُ وَمَنْ فِيهِنَّ ۚ وَإِنْ مِنْ شَيْءٍ إِلَّا يُسَبِّحُ بِحَمْدِهِ وَلَٰكِنْ لَا تَفْقَهُونَ تَسْبِيحَهُمْ ۗ إِنَّهُ كَانَ حَلِيمًا غَفُورًا | The seven heavens glorify Him, and the earth [too], and whoever is in them. There is not a thing but celebrates His praise, but you do not understand their glorification. Indeed, He is all-forbearing, all-forgiving. | Al-Israa : 44
So these things in the world we are use to appear to be physical, but that is part of the deception, and life of this world is but means of deception.
In reality, physical things don't exist, and their nature is in God's vision. So when Isa (a) goes to the spiritual realm, and his body parts come with him, it doesn't mean that realm is physical. It takes a different nature. So when Mohammad (s) when to the heavenly realm, he went to a place Gabriel (a) could not go. So how is Mohammad's (s) body parts supposed to go? They can't if Gabriel (a) cannot and will burn, they will burn too.
Same with Isa (a) he is in a high place near God and his body parts are somewhere there below him and not with him in the spiritual realm, but when he comes back, he will make sure to get them and have same body part, just like Mohammad (s) did when he came back from his night journey from the sacred place of prostration to the furthest place of prostration.