If backside power requires say 10 more imaging steps, then for a given number of imaging machines you can produce fewer wafers per month.
If there is strong demand for the new process (which, since it'll be industry leading I'm sure there will be), you make more money if you can produce more wafers per month but missing a feature.
As demand reduces and more imaging machines get delivered, then it makes sense to add in backside power again.
If backside power requires say 10 more imaging steps, then for a given number of imaging machines you can produce fewer wafers per month.
If there is strong demand for the new process (which, since it'll be industry leading I'm sure there will be), you make more money if you can produce more wafers per month but missing a feature.
As demand reduces and more imaging machines get delivered, then it makes sense to add in backside power again.