The distinction is that the ESP32 doesn't run Linux. Because of that it can be significantly lower performance, and cheaper. All the while still being a very decent miner for ~6 ASICs
IMO BM1397 is still in the sweet spot of price, performance and efficiency (for people who aren't Bitmain). For example the BM1397 has a higher hashrate per chip and is cheaper in small-ish quantities than the BM1398 (S19) and BM1362 (S19J Pro)
I guess the esp's are more than fast enough to handle several asics. I will do some profiling so see what the actual number is.
I think sadly the BM1397 is the last asic suitable for these kind of miners. If you do the math you will find that newer asics need 20A or even 40A to run, and those kind of currents are not easily managed on 2-layer pcb's (or even 4-layers, just look at the current shunts plastered all over antminer hash boards).