I don't think that's correct, not with their road stuff anyway. I'm running a 10 spd rear derailleur with 11spd everything else and it works perfectly. The geo of the derailleurs are the same.
That would mean the gap between the cogs on an 11 speed block is the same as a 10, assuming the shifters do pull the same amount of cable and Len's not telling us porkies.
I don't think the gaps on the block are the same. Len must be telling porkies, as my setup works perfectly! The cable pull must be shorter on the 11spd shifters.
For reference.
Shifters: Force 22
Rear derailleur: Force 10spd
Cassette: Force 22 11-28
I don't think that's correct, not with their road stuff anyway. I'm running a 10 spd rear derailleur with 11spd everything else and it works perfectly. The geo of the derailleurs are the same.