[Sword & Shield] Pokémon Friendship while in PC Box on Sword/Shield?

Lately I've been thinking to max out some of my Pokémon's friendship in Pokémon Sword, hoping that they can get the same perk from Pokémon-Amie or Pokémon Refresh, like having the 'mons shrug off some status problems like paralysis, or even dealing some crits. According to some sources, the friendship mechanic is changed that it can be maxed out by using Camping mechanic. However, this makes me want to ask for one thing.

Back then, even when I played recent titles like X/Y and Sun/Moon, putting some 'mons in PC Box is no problem because the friendship level is still intact, but as I'm juggling on several 'mons to fill some part of my Pokédex and at times on catching spree in Pokémon Sword, I heard from some media that putting some 'mons in PC Box for long may affect their friendship negatively, and this bothers me because I already have about hundreds of 'mons that I'm not sure if I can raise friendship levels for all of them, and I'm also concerned about my current team if I left some of it on PC for long, or when I'm away from playing Pokémon for quite a while.

So I want to ask, is this statement about putting some 'mons on PC Box is true, considering that the friendship mechanic has been changed to max out by camping? Or does the friendship level keep intact despite of long time? (And I hope for the latter, preferably.) This question applies to friendships added through both normal means and also through camping. Thanks in advance.