No, you measure a "low quality" PRIR, and it is possible to that with only a tweeter (because the hrtf differences between individuals will mainly be in the higher frequency range I think). Smyth then (was the plan) can use this PRIR to personalize a high quality non-personal PRIR (BRIR) meaning they create a new PRIR from the first 2 PRIRs that combines the high quality room+speaker sound with a better match to your personal hrtf.
I don't think so. First of all the ManLoud requires your input about what you subjectively think sounds equally loud to you, and what Smyth wants to do is an automated process. Second the ManLoud is effectively changing the HPEQ, applying some additional EQ to the two headphone channels only. The processing of the PRIRs will involve changes to the actual room impulse responses, per virtual speaker, per lookangle, per ear. It would boil down to applying additional EQ per virtual speaker, per lookangle, per ear. (And hence, if it works, has much more potential than a ManLoud). I suspect they will try to isolate the direct sound portion of your personal "low-quality" PRIR, by looking at what happens first in the impulses (direct sound will arrive first) because that will not be influenced by the room - for higher frequencies at least - only by the frequency response of the speaker (maybe the use of their specific tweeter is required of which they know the frequency response).