Wifi is also slower, M1 Macs have only 2x2 MIMO chip (Broadcom BCM4378). In AC mode (5 GHz, HT80), it maxes with 866 Mbps link speed. Intel Macs are faster in this regard.
That said, I wouldn't necessarily expect the 16" MBP to have 3x3 either. Last time I checked, laptop oriented wifi6 3x3 chipsets didn't exist (though something may have shown up in the last few months)
Well, two-port 13" might had 2x2, but touchbar ones never did... So one doesn't know, what to expect, especially since there is no 4-port M1 MBP, as there is no non-touchbar M1 MBP.
Though you might have a point with 3x3 wifi6 chipsets, I didn't do any research whether there are any. Given the way the market went with wifi5 ones - with majority of vendors just using 2x2, this is something I should have expected.
Do theoretical speed limits matter though? Real speeds will be much lower anyway. And if you need consistent high speeds you're likely to use a cabled connection anyway.
I've found out, because wifi was subjectively slower. 5 GHz is nice, because the range is lower, your neighbors are not causing much noise anymore, so the real speeds did approach the theoretical limits (for me; in my environment; using Ubiquity APs, mostly nanoHDs).
Apple used to be one of the vendors, that bothered to put better wifi in their products than competitors; now they fell back to mediocre 2x2 that all the PC vendors use.
One of the first things I did with my new M1 MBP was install the OS update (~2 GB) - it came with 11.0.1 - and Xcode (~12 GB), followed by nice big `brew --cask install ...` that included microsoft-office (~1,5 GB).
When transferring tens of gigabytes over network, one definitely notices when the network speed is less than what it is supposed to be.
https://www.google.com/search?q=m1+usb+speed&oq=m1+usb+speed