I've never seen any check [being made on hand luggage] nor have I ever experienced one myself (I do travel LO on a fairly regular basis). That said, I'll also add that, when travelling with myself, the Mrs's beloved carry-on goes regularly well above the imposed limit and she always gets away with it, including on the DH8 aircraft.
The other day, though, she flew W6 and got fined at the gate
P.S.: welcome to FT.
G