I think it is also the fantasy that they will get accepted into the private inner circle of women and be able to participate in secret, female-only stuff (which they think includes sharing tampons with each other). Posting about tampons on TikTok and other places is part of the fantasy; it's aspirational for other troons watching it, and the troon doing the posting gets pleasure both from building up his fantasy and from knowing that other troons envy his successful womanhood.

In reality, not only is "sharing tampons" a fantasy, but these men will never be accepted into women's inner circles. Not even the handmaidens actually want to hang out with male troons in real life; handmaiden support of brave transwomen extends to commenting enthusiastically on posts to show how enlightened they are, and nothing else. Most men who have already trooned out know this deep down, which is part of why they're so bitter and miserable.