[Asooka]

Over the pandemic I could closely observe three junior developers.

One was hybrid remote / on-prem with on-prem menotring and sadly they turned up not to meet our standards. I don't think the work arrangement impacted them.

One was fully remote with their mentor fully remote as well and we hired them full-time.

One was fully on-prem as much as they could, with a mentor who was almost fully remote. They were also hired full-time.

So my experience is that there is no correlation between bringing junior developers up to speed and exactly where they work from. Communicating face to face and communicating remotely are different and require different skill sets, but that is down to the abilities of the individual mentors assigned to the individual juniors. Or put another way - every combination works best for some people