How often does it flood? If only only occasionally, it should be alright.

Whenever it rains more than an inch. The water stays within the swale though and rarely ever overflows. Just like how you would see a Japanese maple in the wild near bodies of water in Japan, I’m guessing they are able to sense wet spots that they should avoid?

Japanese maples are very sensitive to poor drainage. I would not plant in an area that is likely to retain a lot of moisture, even if only for a couple of days at a time.

yes for a few years it may be OK, however as it grows the roots tend to raise the ground around the tree. Eventually the tree creates a dam and your water flow is hindered