I wouldn't plant any eastern buckeye species in a soil that dried out during the summer.

I planted 3 bareroot whips under a pin oak in late 2016. I mulched the planting area with composted stump grindings from a tree removal at the time of planting, and followed up with shredded leaves and wood chips in 2017 and 2018. They've been doing fine without any supplemental watering. They are near the bottom of a small slope in soil that drains very slowly. Standing water even forms at the bottom of the slope after prolonged rain, but hasnt hurt. 2017 was droughty but they were fine. Seems to suggest that with a soil high in organic material, mulch, and shade, they can handle dry periods. A neighboring nursery has some larger specimens in near full sun with a southeast exposure that look good too, but I dont know if they are watering them regularly.

In other words if a site is not likely to be drying out much if at all then they can live there.

I can't comment on Skip's situation, but where I am some low areas can collect water during the wetter times of year but still dry out during periods of summer drought. So without more information I would not make the assumption that an area that can collect water remains moist even during periods of drought.

That is exactly the situation in my yard. Late winter there are ponds and mud, and by late summer the soil is dry and as hard as concrete.