Also my understanding is that the criteria for being allowed to stay doesn't differentiate on the level of the degree. For instance, Phd students who have completed their course work but are busy working on their thesis and building their publishing record are royally screwed. I expect a number of transfers of some of the best and brightest to research universities in Canada and Europe. I personally witnessed how much of a boon the mistreatment of Iranian students by the US govt. was to universities in Canada. They got some of the best and brightest who would have otherwise been gobbled up by top schools in the US.
I expect a massive and permanent exodus of foreign students to other countries with more pragmatic policies in place.
I also find it funny that you bring up Canada as Canadian schools openly discriminate against international students thanks to government policies.
But that's the part that people are upset about. People aren't angry that there exists a policy to prevent students of fully online universities from getting visas.
People are upset that because it is completely reasonable for a traditional brick-and-mortar university to run classes 100% online this coming semester (e.g., Harvard) and that suddenly a bunch of students who are attending Harvard and have been doing so for years are forced to leave the country on a moment's notice.
What nuance is there? The original exception (you can take 100% online classes) was thoroughly reasonable given the pandemic and the new updated policy is completely unreasonable. It only harms people and benefits no one.