Sprint planning takes 30 minutes for our team too. And exactly like OP, backlog grooming is done during 1-1s with leads.

I am sorry if you find it that much hard to believe.

By the time we're in planning, only things to discuss is estimation and priority, it takes virtually no time. We have a whole hour booked and spend half of it to just hang out, pretty much the only time where the whole team is present in one meeting.

What they described isn't different of how it worked in my previous two companies that used Jira...