Yeah, you got that the other way around. Having stereo speakers, even on smaller devices, makes a big difference when it comes to the quality of the audio-output.
I’ve been listening to podcasts (as well as the ocasional music video and TV series) from my home country on a daily basis, for years, often only using the phone’s speakers. My old iPhone X and XS, although also great, stereo speakers are actually slightly worse than the Mini’s, despite the smaller form factor of the Mini. Either you haven’t actually tried a 12 mini, or you tried one with faulty speakers. Either way, your comment makes zero sense.