I was thinking the same thing. Thinking about it logically, wouldn't he just skip a meal at 7pm on a Sunday with the staff and team mates, if he was "legless"?
The guy filming it set the narrative that he wanted, because he saw a brief loss of balance as someone pulled his arm. He jumped all over it and has got all the attention he wanted(it went viral).
It could have been anything: A short loss of balance(ie nothing), maybe he was just knackered, maybe he'd had some physio or treatment that day that affected his legs(maybe Pep knows that), maybe he'd been vaping the Mary Jane before heading out for dinner(although with the random testing these days, I don't know if it's safe for them to do that). Or maybe he was just a little tipsy and I'm not sure that matters. I understand he's cost the club a lot of money and is paid a lot but he's still only human and a young man to boot. With the pressure he's under, I understand why he might want to self-medicate, that can actually be healthier than doing nothing about it(stress, anxiety etc).
There's no signs of him being "off the rails" in that video to my eyes, either way. You'd think the other video of him interacting with a fan, that also went viral, would have added some balance. I think he's making a real effort, personally.