One other thing about this.... not to muddy the waters... but, there are various "cognitive burdens" when playing. And different people will experience those burdens to a greater or lesser degree... We can all (and should!) train ourselves to listen while playing, whether reading or not.
But if we're reading while playing, there is necessarily going to be some amount of "cognitive burden," some amount or our attention taken up from reading, even for comfortable readers. So I think one key point of this thread (not to put words into @twocats 's mouth)... is that, for those of us who are habitual readers, what can we gain from memorizing. And I think this idea that, if we memorize and are therefore not reading the score, we will be freed up, our attention will be freed up, to focus more on other things... so it's not that we're not listening to tone while reading, but the idea anyway, is that we could listen more closely or fully if we memorize....
Now, having said all that.... since I am a comfortable reader and I almost never memorize, it might be the case that my ability to listen could actually be diminished when I'm trying to play from memory, because the cognitive burden of memorizing will be so much higher for me, compared to when I'm reading...
This of course is something to experiment with (in the spirit of MG), and is unlikely to be the same from one pianist to the next....