biblatex is ignoring maxcitenames

The default in biblatex is to use the uniquelist option. APA style also uses this. This option dynamically changes the maxnames/minnames settings in order to make citations unique. This is required by APA. APA style also applies APA rules regarding citation list truncation after the first cite within a paragraph. You are probably noticing the effects of these settings. APA style with maxnames=2 is essentially not APA style – these settings are partly hard-coded into the style as a result ...

The solution I found was to replace citestyle=apa with citestyle=authoryear. This fixes the problem.