my 12 batch 1s can all run at 750Mhz and in my setup range from a stable 63C to 74C across them; a lot of variance.
2 of mine run fastest at 725Mhz.

All of them run "best" at 700Mhz or less -- best is a combination of heat vs. hashrate.

At max (750), mine do a stable 192kSol/sec with variance up to ~195.

At 700Mhz, mine do a stable 186kSol/sec with temps in a managable 72C or less.

My setup: https://imgur.com/a/6SBUt2S

(copying my setup as is would be a bad idea for reasons I don't have time to get into at the moment, but you cannot egress 1000cfm out of your house without other problems...).

The most ideal configuration is for 650Mhz across all of mine -- they are stable and cool with minimal (relative) airflow across them (and thus minimal impact to the house environment).

My point here is... even though I can make the batch1s not crash at 750Mhz, that isn't their ideal point. Any unit alone, I can get to 725/750, but when  I combine them all together and their heat impacts each other, 650-700 is ideal with minimal 'loss' in hashrate.
... Which puts them in line with the ~681mhz folk are seeing now.

Once my Z9s come in, I'll see how those chips work in comparison....

-j