I can reproduce this behavior. It only occurs when the only tax code selected is a single-component code. If both single- and multi-component codes are used, both are displayed:
Likewise, if some items are tax-exempt, the various codes are all listed:
The only situation where the
Tax column does not appear is when all items on the invoice are subject to the same, single-component tax. Then, only the tax code and amount applied in the totals section appears. But as a result, there is no possibility of ambiguity. I think all legal requirements are satisfied.