On my most recent intercontinental flights 2 weeks ago, my boarding pass also stated the necessity to be checked-in (or baggage dropped off actually) 180 minutes before departure. I ignored this of course, and arrived very early (in my experience) with 110 minutes to spare.

I wasn't told off or scowled at.

When I asked about the 180 minutes, the check-in agent stated it has become standard, especially during the busy summer holidays, so that more people show up earlier, while the frequent fliers will presumably still arrive at least an one in advance. Makes sense to me.