It looks like Detail Armor Bar does not take into account absorption hearts being on their own row, when Mantle (a Tinkers' Construct dependency) is set to displays extra regular hearts as a single row (which is the default). The armor bar simply overlaps the absorption hearts. When compatibility mode is off, the armor bar is offset as usual.

Screenshot

With compatibility mode off:

With compatibility mode on:

Still relevant, this also happens for colorful hearts. Either there is a gap because the mod is removing new health rows, or the armor ignores absorption.