Or so says a representative of Canon, a company that still has most of its eggs in the SLR basket. The arguments offered are vague amd not very persuasive, and even the claim seems to have come only after some pro-SLR egging on from the interviewer.
I think they're pretty persuasive, as it's about optics not electronics, if I understand correctly you basically have two different-focused images simultaneously which is fine when you don't need to present a single image, but not so good if you have it on the image sensor, and with only one image focused you don't have enough information.
Of course someone may invent some new sort of workaround, or the current image sensor phase detect gets "good enough", so it's not written in stone. I think though that SLRs will be number one high end action camera for many years still. We'll see.
