Errr, that is not correct
There is no such thing as a "Sarawak state-controlled IPTAs"
The Sarawak government does 'own' some IPTS'es like Swinburne Sarawak, Curtin Miri, University Technology Sarawak, etc.
But make no mistake, these are very much IPTS'es, with according fee levels. But they accept UEC as one of the qualifications that an applicant can use to enter Swinburne Sarawak/Curtin Miri/University Technology Sarawak. After paying IPTS level fees.
Which are very much more expensive than UNIMAS and UiTM Sarawak, the IPTA's physically located in Sarawak.
Selangor also has their own state owned university, UNISEL, which yes, does accept UEC as a entry qualification. But UNISEL is very much a IPTS.
As to why Penang doesn't have a state owned university, that is a question for their people to ask their government.
Thanks for the enlightenment. If that's the case, then I don't see much difference since almost all IPTS in the country do recognise the UEC cert.