The way i’m seeing this is: OP is asking whether using larger social media platforms as a shield would make this content permissible. There’s what appears to be existing unofficial precedent (nsfw) suggesting this is the case so far in different circumstances, but in that instance i think it could end up as a debate on whether childbirth is a “questionable situation” regarding the child (assuming there’s no questionable posing involved).

I couldn’t find evidence of Yuli Kruchkova somehow coercing Mari into producing the videos on the example content’s channel, which weighs against the “questionable situation” argument here. Both channels appear to focus the majority of the videos into fitness content rather than fashion, weighing against the “child model” part of the rule.

This leaves out 2 questions - whether a channel focused on fitness can fall subject to the “questionable poses” part, and whether the comments section is enough to make it fall into the “junior idols” part of the rule. Within the childbirth community’s precedent context, this happens to not be the case, so assuming the “questionable poses” part is ignored for purposes of discussion i’d weigh towards allowing the example content so long as there’s no focus towards the “junior idols” part.