When I first accepted my gender identity and started to think of transitioning, I thought I'll go as far as HRT without coming out / going full-time / social transition etc. I simply looked at it as a way to put my brain at peace without needing to do anything else. Ideally, I would want to go all the way and live the life of a cis female, but that is not fully possible, and even what is possible is difficult because of my having a wife, career, family and friends that I do not want to lose.
Actually, even HRT is difficult because of how it may affect my relationship with my wife, and possibly how I behave otherwise as well, but I thought I could work all that out and still go for HRT without social transition.
However, as I have seen on this forum and elsewhere, there may be many unexpected changes from HRT, sometimes even low-dose. I am young enough, already have some feminine features, and resemble my mom a little too much, so being on HRT and expecting to pass as male even after a year or so may become very difficult. Yes, I could probably manage it with short hair, a stubble and my male voice, but then I am already growing my hair and I like it, I am already considering facial hair removal with no possibility of HRT for at least a year or so, and my male voice will only help when I start talking, not otherwise.
So I think HRT without social transition may be an option for some people, but probably not for me. If I do go ahead with HRT and do not reach the 'male-fail' point for long or maybe ever, I may end up not transitioning socially, but it seems highly unlikely.