No, it was definitely possible.
They went SOFT -> SOFT -> MEDIUM? If so, shouldn't they have gone SOFT -> MEDIUM? That's the point I want to make. Some people here seemed to think Gasly was on a ONE stopper, which they are mistaken. Had Gasly's second set been mediums, he might have somehow finished in front of or behind Vettel. Gasly is good with tires and doing long stints and had he been on the mediums 2nd stint he probably wouldn't have dropped back so much. Gasly also had a very long pit stop with the left rear causing issues. 39 laps on the soft tire(2 stints 10 and 29 laps respectively) and 17 (only really 15 laps racing) on the mediums. I suppose one rationale is that they were using Gasly to better learn/understand the soft tires.