In 2021, in the MLB, the top batting average was .328. The person at #50 was at .271 and there were 2 under .200 in the top 132. They require minimum 3.1 plate appearances per game to be rated. Team batting averages ranged from .226 to .267 with only 5 being over .250.
The NCAA D1 stats site shows only the top 151 with the highest being .600 (Danielle Gibson of Arkansas) and the lowest is .419. That includes some people with only a few games and PA though. A lot of the list list not would qualify to be listed in MLB, but since games are shorter we can use at least 2.4 per game (3.1/9*7). That leaves us with 139 out of 151. Their average is .460 (5300 PA, 2439 HITS) and their average PA is 3.01. Note that I am fudging some as PA is only AB count in this which doesn't include walks and other things so a few others may qualify. Out of 291 teams listed with batting averages on the NCAA website: 265 are over .200, 171 are over .250, 57 are over .300, and 22 are over .333.
I would say the Mendoza Line has to be higher in NCAA Softball. The line looks like it might need to be a .300 or higher.