Tow vehicle tire size not to spec

I'm looking to replace the tires on my tow vehicle (2010 Ford Expedition) and I was surprised to learn that my existing tires do NOT match the tires specs on the vehicle placard. I don't know when or why that happenend. Anyways...

Placard specs are P255/70R18
Existing tires are P265/70R18

The wifes 2016 1500 chevy crew cab short bed 5.3 engine 6 speed tranny aluminum wheels came with P255/70-17" tires.
After 42k miles it was time to replace them.
The 255/70 size doesn't have a very big selection in the tread type/design I use.
The P265/70-17 has a huge selection so went with the P265/70 size in the tread design I wanted.

No difference in mpgs.
No difference in towing performance pulling a 10k car hauler with various equipment on the deck.
No difference in braking.
No issues with matching wheel width vs tire tread width
There simply isn't that big of a difference in a 255 vs a 265 tire to cause issues for my use.
More than likely your previous owner found the same thing when his tire replacement time came.