Row and column backgrounds are woven in a strange way

[Tuplanolla]

Versions

Coq 8.15.0

Coqtail 1.6.2

Vim 8.2

Equations 1.3

Python 3.7.4

Description

This is not so much of a bug as it is a peculiar interaction of features, but it is quite strange how row and column background colors fight for supremacy. Checking Coq's own theories/Arith/PeanoNat.v with a rainbow color scheme looks as follows.

[whonore]

The blue from CoqtailChecked comes from matchadd and :h matchadd says "[...] regardless of the chosen priority a match will always overrule syntax highlighting" so it I think it should win over hl-CursorColumn and friends. The weird thing is where it seems to behave inconsistently like how the green column sometimes shows through where there’s a space or a ., but not always (line 158 + 7 vs 158 - 6).