Requesting something and something actually happening are two very different things.
There is also a meaningful difference between an in-person group chat and a group chat that will remain visible to the whole team for months or years to come.
This request becomes far more than just changing the medium, and requires everyone involved to adjust to the idea that everything they ask can be later analyzed without the context of the moment, and this has a chilling effect on the kinds of things that people are willing to ask. This in turn fundamentally changes the dynamic into something that doesn’t really replace the original junior/senior relationship effectively.
Accomplishing what the parent comment is talking about requires far more than “please use the group chat”.