Wait does Bocchi wear the tracksuit to hide her body specifically? It's been a minute so my memory is hazy. To my knowledge it's pretty common in anime for it to be the easy choice of lounge wear for lazy characters / shut ins. Looking through things I saw a a Reddit post saying she wears one because of falling down, also a 2016 MAL forum post about Hikkikomori characters wearing tracksuits. Though I'd say aside from Hikkikomori characters you have NEETs. Plus two examples off the top off my head that even came after 2016 are, Gabriel from Gabriel DropOut using a Track Jacket and going bottomless as her choice of lazy gaming wear, and Miyako Hoshino from An Angel Flew Down to Me wears a tracksuit as her at home lounge wear.
Which I mean if people interpret Bocchi as wearing a tracksuit because of dysphoria related reasons fair enough. As I was saying before everyone's interpretation is valid. For me it's a common trope with Japanese media and Bocchi is relatable for everyone with social anxiety and so fourth. I'm not trans myself and I think Bocchi is extremely relatable, and I also think if there's specific elements that trans people find relatable to their experiences that's cool. I think Bocchi being relatable for different people and a variety of different experiences with isolation and alienation is part of why she's a great character.