Sometime I wondering if Canon & Nikon deliberately "tinker" with their firmware updates to make third party lenses not to auto focus quicker or introduce some other bug to basically not make them work as well as they should. I say this because two years ago I had Tamron 18-50 f/2.8 OS that used to work brilliantly with my EOS 60D but once I updated my firmware the lens became slower at auto focusing.
From Canon's and Nikon's perspective, "work as well as they should" means "not at all" because at least Canon to my knowledge makes no effort at all to help 3rd party gear work. On the contrary - with each new body or protocol update you might be out of luck, and of course this is a major selling point for "original" gear.
But this is the first time I've head someone say Canon but regressions in their firmware deliberately - but it's known to happen, remember how Microsoft drove Novell out of the DOS business by engineering false warnings into Windows 3.1. Years later and having seen the source code courts decided against MS, but too late for Novell to recover...
I can't authenticate my suspicion but I feel it is quite possible because a similar thing happened to my Nikon D700 with my "Bigma" 50-500 (non OS) lens I both sold now(D700 partially funded my 5D MK III).
5D MK III, 16-35/2.8 L II, 24-70/2.8 VC, 24-105/4 L IS, 70-200/2.8 L IS II, 100/2.8 L IS, 40/2.8, 50/1.4, 85/1.8, 150-500 OS, 600EX-RTx2, ST-E3-RT, Rokinon 24/3.5 T-S, D7100+18-300 VR, YN568EX, 055CXPRO4+468MGRC2, 190CXPRO4+322RC2, Gorillapod Focus+496RC2, CamRanger, B+W filters, Konova K3/31.5 etc