I would go by what Disney officially says for pregnancy. If it was at all a safety situation, Disney would recommend pregnant women avoid it.
One of the problems with the allears site is that the information is from surveys people fill out on their website, but you have no idea why they thought it was not a good ride for someone with that situation. I know I filled out several surveys regarding disabilities on the site and you had to choose a best and worst ride for each park. You had to choose to go to the next question and there was not a space to explain why.
For Maelstrom, it could be that some women late in pregnancy found it difficult to get into the seats, or felt the seats were uncomfortable for them, or for part of the ride, you are facing backwards - maybe some peole found they had motion sickness from doing that. It's hard to say.