This is a "step above" the process that I think that I am using. Being a long time bass clarinet player (and a soprano horn player for almost as long), I can "think through" such concepts far better when they are mechanically related. Since the only difference is the missing register key (at the early level), it's a lot easier to work through than note names and their correspondence.
From the reception that this little trick has received over the years, it appears that I'm not alone in this regard. And, for those of us who are "up in years" (I'm pushing sixty these days), new concepts are always harder to absorb. Using something that is habituated (i.e., pounded into the hind brain through many years of practice starting early) is always going to work better for old folks than is some "non-mnenoic" method.
This habituation theory was best seen in an old James Burke television program. (He's the Brit who put together the Connections series back in the 1980's.) In the program dealing with the human brain, he illustrated how the "hind brain" takes over various "lower level" activities as long as they are acquired early on. Hooked up to an electroenchepilograph - er, a "brain wave" machine, he showed us what happened when a novice tried to play guitar: in that case, the activity in the brain was centered in the frontal lobes. Then he did the same thing, only talking while playing. In that case, his hind brain was dealing with the "housekeeping" activity of guitar playing while his frontal lobes were dealing with the narration.
While not privy to all that went on with that program, I do know that I can play some instruments (those of long, long acquaintance, like the bass clarinet), performing on them musically the whole while, and yet have the spare mental processing capacity to think about something else completely different (like lunch or bill paying), all without any misstep. In contrast, I try to do the same thing on bassoon, I collapse into a mental wreck, and doing neither activity well in the bargain.
Over the years, I've picked up just enough musical theory to be a danger to myself, and thinking in intervals just hasn't worked - for me. That's not to say that it won't work for others, just that this offers an alternate method for those not up to the mental gymnastics for the "normal" way of doing it.
(And, for the record, I use the classic "read the bottom of the notes" method for A to Bb transposition, and the not-so-classical "set the interval at the start of the phrase and then play the tune" when making the C to Bb jump. Of course, the first is of dubious utility, since I've owned an excellent A clarinet for about thirty years. The second still comes in handy, although it was last used some seven years ago.)
The Stubbins book covers all of these, plus a lot more, In my eyes, it's almost as useful as the Rendall book, but not up to the level of the Kroll book when it comes to clarinet playing, history, and techniques. By way of comparison, I prefer all of these to the book by Pino.