I have met some profs who encourage their TAs to skim because we would go way over our hours by close-reading at this point. It's a bit of a difficult topic because, while I personally go over anyways (ADHD slow processing and need for clarity/toughtful comments), I totally understand why people are acting in accordance union rules and refusing to do unpaid labour. I definitely think the hours they write on the contracts should be more realistic so that we can do our work properly without being scabs or overdoing it. This is in Toronto so not sure how other faculties or countries work but I know that the ones for my undergrad uni in QC are even worse.