The following is just my personal speculation.
It was the 1920s, Atanu. That was a time when America was Christian, and far more people knew their bibles inside out than they do today. Like all good teachers, he taught to his audience. Of course he was a Hindu. But he was a Hindu teaching Christians, so the method of teaching changed. In order for the audience to understand anything at all, he had to find parallels, and he found those parallels in the Christian bible. That was the way they understood him. I'd be interested if there was a transcribed talk of his around the same time given in India. My bet is that if he was speaking to Hindus, it would be much more in the context of Hinduism, a language his audience at that time would understand.
Same goes for the book. It was written directed at a primarily Christian audience, and like all good writers, he knew his audience. Most writers are quite aware of audience.
Today, nearly 100 years later, I suspect, things would be different. Deepak Chopra knows his audience. He's addressing secularists primarily. People disillusioned with mass consciousness of the day, same as back then.
Yogananda passed before I was born. It was 1952, over 60 years ago. The famous book was published in 1946, nearly 70 years ago. Times have changed, and as with other institutions, I'm sure SRF has changed. How exactly, I have no idea. There are only a handful of direct disciples left. They too are passing on.
Also, these days far more people are willing to jump straight into Hinduism, because unlike back then, they have little or no Christian subconscious programming. Still their is other stuff to overcome (like atheism, drug-culture, and materialism).
But this is just my take. I hope I'm not making you angry again.