First of all, he wasn't required to move out of the province. The laws of the province are as they are and he chose not to deal with them by studying elsewhere. This seems to have been his choice from what you describe.
And what you describe would happen in a two state solution anyway, getting more independence wouldn't mean the end of language laws. I don't see any sense in letting people slip through the law because they supposedly don't intend in staying in Quebec after. All immigrants would start saying ''they're just here a few years anyway''...
The reason we expect immigrants to learn French is for them to integrate and be active members of Quebec society.
First off, he'd never applied as an immigrant but was in Canada on a tourist visa initially, which was then changed to a student visa. So immigration has nothing to do with this.
Now as for Quebec's language laws, yes I agree they would not necessarily change after separation, and that he'd still have had to move out. Maintaining close ties though would at least give the option of leaving for Ontario. Total separation would remove that option.
And I'll just reply to something JLM mentioned too, about people from Gatineau working for the Federal government in Ottawa. I'd met an Ontarian once who'd married a Quebecer, settled in Charlevoix, and ended up working in the medical field for the Quebec provincial government.
In principle, this policy would continue to allow Canadians to seek such employment in Quebec if they wanted it. So it would still benefit English-Canadians too. Besides, how do you know there are no doctors living in Ottawa and working in Gatineau?