Can anyone provide an explanation of the NYC PTET Changes?

NYC Mayor has proposed that the PTET credit be reduced to 75% calling it a loophole for high income earners that allow them to reduce their federal income liability. He claims that reducing the PTET credit will raise $740 million (or a billion depending on you source) dollars for NYC.

So anyway how is that going to work? ABC Partnership pays $15,000 in PTET payments to NYC but the partner(s) only get $11,250 in NYC credit?? So they still owe $3,750? So, the theory is that you've paid $18,750 in tax on a $15,000 bill netting NYC $3,750? Clearly insane.

Alternatively, I don't see how reducing the allowable federal expense makes NYC any money. How does reducing the amount of the federal expense allowable for PTET payments increase NYC tax receipts? In all cases NYC taxes paid are an addback to income when determining taxes owed, thus avoiding the deathloop.

Genuinely, what am I missing?