i don't think you have the right to explain, gently or otherwise, that losing a baby is devastating and heartbreaking whenever it happens. that's your perception, to coin a phrase, and that woman may quite legitimately go to her grave believing that you have been through something less traumatic than she.
and remember, for some people it's not devastating (viz bonsoir and other people i know) and expecting them to be heartbroken etc may well be insensitive to their needs. plenty of people do come to a reckoning that what happened was 'for the best', no matter how insensitive that remark has been portrayed here.
in a way, i think you might subconsciously be as guilty as the people in the group of 'competifying' grief, if you can't see that those women might quite legitimately think that what you were luckier than they were. i simply do not believe that at some level women who lost their babies later don't feel less fortunate than those of us who lost them earlier, and that, imo, is quite fair enough. i think it's human nature to compare.
although i would stress that the woman didn't say that it was 'easier' by your own telling, she said 'easier to understand'. presumably she meant in terms of medical conditions, development etc and because you wouldn't have yet assumed you were out of the woods.
it must be an absolute torture (speaking as the mum of a prem) for women who lost children really late on to think that had they only been 'out' they might have been safe. i can be 100% certain that my child would have died in utero within a few days, had i not been scanned and operated on that afternoon, and i thank god that i was, but you will never in a million years persuade me that had i lost her then it would have been the same as when i lost my other pregnancies (and remember, i was so miserable then that i feared or my sanity). believe me, i would have experienced paroxysms of grief that would have topped anything i'd ever have experienced before.
as i have said before, even if one's sense of grief might be the same, that does not mean that the traumatic event that precipitated it might not be harder on a number of levels. it's a quantum, the two things can exist simultaneously imo. i do think that you need to consider that, tbh, if your group is to be successful and helpful to others.
i like kewk's point that any comment in the midst of that grief is forgiveable, but i do think that even if those women come out of the other side of that grief and still feel the same, it's not up to you to tell them different, however gently, because then you're just falling into the same trap as they are.
i just don't like the way that they have been portrayed as being insensitive or foolish for having said that your loss was 'easier to understand', especially given that they are sunk deep in the midst of their own loss. it seems a really unfair characterisation to me, and i think those were the answers you were after, tbh, when you posted in aibu. i just wonder whether you're ready to look after the group or will be able to help them in future if you come on here encouraging people to dismiss their feelings on your behalf. are you sure you really are ready to take on other people's pain? (i must stress that i mean this in a nice way, however tough it sounds. it's actually a very confrontational question that you've asked, if you think about it.)