Late to retract landing gear

I did a flight today from Heathrow to Jeddah on a BA 787-9 and just before take off the pilot made an announcement that I thought was that one of the landing gear doors had a fault so they wouldn’t retract it until 10 minutes into the flight. Someone I travelled with thought the announcement was that all the gear would remain down for 10 minutes.

Either way, 10 minutes in, about 13,000 feet, we heard the whirring and clunk as something was retracted and felt a bump as it did.

Does anyone know why this would be? I’ve heard of gear being left down for a bit longer than usual to cool brakes or let a wheel stop spinning but I can’t think why they would need to leave anything open for 10 minutes and I’m just curious if anyone has any ideas?

We did wonder if it would be easier to retract gear at 13,000 feet than 1,000 but then I would have thought the higher air speed offsets the lower air pressure and probably makes it just as hard.

No matter what, though, they wouldn’t want to exceed VLE with the gear down. They’d be slowest just after takeoff so forces should be lower and it would make sense to raise gear then but that’s really odd to wait. Would be interesting to know why they did that. If they anticipated gear door issues they shouldn’t have taken off. Mystery to me.

First things First, when the gear is down, it creates drag. That’s why the Landing gear can extend and retract.
To answer your question, I have no Idea. Maybe they were working with it in the cockpit, but that’s just a guess.
Do Any Pilots Know Why This Would Be!?!