All presidents have an approved list of friendly journalists. And those interested in only trouble; this goes back to 1895 or earlier. There’s no evidence Biden is “allowed” to do something. This is a routine compilation that staffer and aides help the president craft. In any administration.
But if you’re looking for an in-depth study of a president who not only refused certain questions but told reporters they were stupid, stormed out of press briefings and cancelled them mid-way, feel free to check out any of the reading material below. Trump changed the relationship dynamics between the WH and the media for the foreseeable future.
I think what you’ll find is that you shouldn’t ask why Biden’s treated differently – you should’ve asked whether it was even true.
https://money.cnn.com/2016/06/14/media/donald-trump-media-blacklist/
https://www.cjr.org/the_media_today/white-house-press-passes.php
https://www.newyorker.com/news/news-desk/can-the-white-house-pick-its-press
https://www.theguardian.com/us-news/2017/feb/24/media-blocked-white-house-briefing-sean-spicer