Well, you have to remember that Mr. Stuart is acting as a salesman here, and like most salesmen he'll try to tell you enough to buy his product but not nearly enough for you to make that product yourself (so you need to buy it from him if you want it). Nevertheless, I see the same points being made (by him). 1) you need the whole process - MQA encoding after the ADC, then MQA decoding in the DAC, 2) a minimum-phase filter (characteristics not exactly specified LOL) is important and 3) eliminating errors in the time-domain (as opposed to the frequency domain, where attention has usually been focused, according to Mr. Stuart) is of major importance in accurately reproducing the sound on the master recording.
A couple of other points. First, it's a proprietary process, and it's in Meridian's interest (although not at all in our interest) to tell us as little as possible while still convincing us to buy into it (and buy it). Second, the process is applied to existing digital master recordings (so far, mostly but not exclusively, to recordings originally recorded on analog tape and then converted to hi-res PCM digital), so this all begs the question of why other engineers wouldn't be able to design DAC's which could accomplish the same thing (or better?) without using MQA?