In general I think it's bad if your workplace is "volunteering you for" something, do they not ask you first? They just tell you that you have to do it? I think that when you said you were returning to work they assumed you'd be returning to your full role and responsibilities, so I don't think they were targeting you or trying to be insensitive per se. If you need to ease into things, totally understandable, you should communicate that. But regardless of the situation being assigned to something without asking would put me off, idk if that is the norm in other jobs.