What you are describing is what is supposed to happen. What actually happens is that big film studios ignore the center channel altogether. Instead choosing to mix the voice in 3D because cinema and IMAX and Dolby, etc. which honestly sounds extraordinary in those sound system. It is mostly because they are desperate to propose something that actually brings a competitive edge to theaters against home TVs and streaming. Instead of, you know, making good films. But that’s beside the point.

What ends up happening is that your system’s codecs and down mixers do what they are told they are supposed to do. Mix all channels together into stereo, with a tiny boost to the center channel on both sides. Easy, that should bring forward the dialogue, whoops! there’s no dialogue in the center channel, it is all mushed all over the place over the other 4 channels and drowned out by the audio FX.

This is the reason some egregiously poorly dialogue mixed movies like Tenet and The Dark Knight Rises actually also sounded bad in mid to lower tier theaters. Those theaters were calibrated for exactly the way it was supposed to sound, with a strong center channel for dialogue and what is directly in front of the camera. But the audio isn’t there, it is dispersed to a side in the other two speakers (this is done automatically now in mixing software, which doesn’t help). The movie came with the flaw, and even if you have a good 5.1 channel audio at home, you can check for yourself, the dialogue is also hard to hear on those movies. Because it was shit from the beginning unless you hear it in an IMAX theater or have access to one of those 3D field Dolby Atmos 64 speaker systems that Nolan mixes on.