> BUT the new time they unlock will be spent doing more of the mundane work

...which will also quickly be done by "AI", uncovering more such tasks until most of the "mundane work" is done by "AI" leaving humans free to do "non-mundane work". Of course those less mundane tasks require more insight, intelligence, knowledge and initiative from those humans which means some people will just not be able to keep up with their competitors, the humans who can do the less mundane tasks and the "AI" which can do the mundane stuff faster, more reliably and cheaper.

The big question is what those humans will do once such a scenario becomes true.