I wouldn't be so confident without actual evidence. The memory boards on the 11" and 13" machines have different part numbers and are oriented 180-degrees differently. They may be identical and/or compatible, but a few thousand dollars in purchase is not an easy thing to drop on an assumption.
In my experience disassembling most of Apple's laptops, the things they do not standardize between models are absurd.
I would either wait for someone to test it out first, or roll the dice and try it yourself.
Good luck!