It still seems like you're comparing a datetime value (mba_run_dtm), which is represented as a number, to a string literal.
In database-specific SQL, that might work. But I'm not sure that the literal value in FEDSQL is converted to a legit datetime for comparison. It feels like you still need to do something to convert that '2018-05-11 19:51:09.744' value to native value. Maybe you need to add the TIMESTAMP keyword:
proc fedsql libs=(mba mbadsa);
SELECT count(*) from mba.dsa.equifax_das_scr where
mba_run_dtm > TIMESTAMP&equifax_data_date;
quit;
(Not an expert on FEDQL here...but learning...)
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