Considering the current shortage of Whatman filters, is there any reason why filters from another manufacturer couldn't be used as long as the specs are comparable?
No. But I would check them very carefully. Whitmans have a excellent rep and there are a lot of knockoffs. Just remember to check for:
1. sterility, is it sterile or do you have to sterilize it.
2. pore size and grade, make sure there comparible to the whitmans.
3 Chem resistance. Make sure the the BA,BB and such will not melt it.
4. Prefilter. (not sure on this but I believe the whitmans have it and those that don't do not last very long).