Yes I agree.
To clarify, I was away on vacation at the time and we only spoke briefly. We discussed that the lack of details about the severance was weird but we had 10+ reports of others who had received 1-2 months of severance, and they had worked there only a year or two, whereas he had been there 4 years. So we though it was reasonable he would get at least a month of severance, based on precedence of "lesser" employees.
He was told that hr had a standard formula for calculating the severance but was not told that the main factor was his manager's discretion.
Also for him at this time, any money was better than no money, and he was interested in moving on with his life rather than writing a shitty Glassdoor review (he's actually doing much, much better for himself than he was at the prior company, I'm just pissed about the way he was treated).
So yes, this was bad advice and I learned an important lesson. But I'm also thankful it worked out in his favor in the end.