Several Scholars have asserted
You were asked to cite scholars, not claim to know what "several have asserted." Can you name two experts within the past 100 years who have stated that the reference to "James, the brother of Jesus, called the christ" was "unknown until the 4th century?"
Philo's silence itself is an evidence that Josephus' references to Jesus were forgeries.
Hardly. John the Baptist is mentioned by Josephus, and is in the NT, but is found nowhere in Philo. Paul of Tarsus is mentioned nowhere outside of christian literature (not by Philo or Josephus, or the romans) yet we have his letters. Rabbi Hillel is not mentioned by the pharisee Josephus. And so on.
The absence of the mention of a historical figure by one source says nothing about the mention of that figure in another source.