Yeah, that is because it matches to an indexed edge, by closest points - when you split the edge, the added edge is indexed to be the short one on the left, by the look of it, and the entire matched edge is sucked over to the closest point on that edge - which in this case is that corner.
I’ll add this to the pile, but I think it is on there in various forms - I do not know how fixable that is - I lobbied for breaking history in these cases in preference to making something stupid, I may try to revive that campaign. RH-62959 MatchSrf: Matched surface will be distorted after trimming