This is a known limitation of TextCore (used by IMGUI text fields), in 2022.x. 2023+ removes this limitation. The fix, however is not simple and is too risky to backport to 2022.
Note, also, that even in 2021, as far as I know, the limitation was still there. Text would just be cut off at the end after too many characters. The only difference was that there was no error to let you know this was happening.