I would say H1B folks could be a huge threat, coz their volume is quite high. Clearing the IELTS and other requirements must be relatively easy for them, when compared to an applicant from their home country and PPR processing is super fast for H1B applicants as they have already underwent all scrutiny with their H1B.
So I'd say yes their scores should be higher than the cut-off mostly.
This H1B --> CIC trend has hit the roofs because of the new rules H1B imposed in Feb. Just use the below link to check the availability to give an IELTS exam, we are just in March and Jul/Aug is the next available slot at most centers in US.
https://ieltsregistration.org/ielts-candidate/candidateonline/home.html
The next couple of draws should give a clear picture.