I think I figured it out. For anyone else who may be confused about UHRSWORKORG:
According to ipums, the universe for UHRSWORKORG is employed civilians 15+ in the ORGs who were paid by the hour. But confusingly, those who are “paid by the hour” in this case isn’t determined by the variable PAIDHOUR.
In IPUMS, UHRSWORKORG corresponds to the variable PEERNHRO in the basic monthly CPS, which is usual hours for those who reported that they were paid hourly PEERNPER = 1 in the basic monthly.
But in the basic monthly CPS, people who are not paid hourly are then asked, “EVEN THOUGH YOU TOLD ME IT IS EASIER TO REPORT YOUR EARNINGS (PERIODICITY); ARE YOU PAID AT AN HOURLY RATE ON YOUR (MAIN/THIS) JOB?” This is in the CPS basic monthly variable PEERNRT.
I think that the IPUMS variable PAIDHOUR is determined by both of these questions in the basic monthly. I.e., PAIDHOUR == 2 for anyone who reports either being paid hourly, or paid at an hourly rate. But the universe for UHRSWORKORG is only those people who report being paid hourly.