I did listen to Norah Jones SACD a few times and didn't hear anything unusual. When I have more free time I may move them upstairs and compare them side by side with the Focal again (did that before). It may be possible that because I use them with a sub with crossover set to 80, 90 or 100 Hz, the effect you noticed might have been reduced due to lesser cone movement. Again, time permitting I will do more serious listening running them full range.
If you remember, I mentioned that I made up my mind on the LS50 after I auditioned the Blades and learnt that the LS50 employed the same technology.
KEF has been using coaxial design for ages so one would expect they do how to do it well. It is interesting to see the KEF website groups the LS50 with the flagship Muron and Blade, very smart marketing strategy!!
https://www.kefdirect.com/speakers/flagship-hi-fi-speakers.html