For quick processing and to check out the SNR boost I binned the data to the lowest preset, 25%. SVD did not seem to take kindly to that, and results were poor despite trying several combinations of sample stars. No worries, for this, synthetic should be fine. I turned sampled iterations to OFF, and started working on my synthetic iterations and radius. However, it would not come out of Circle of Confusion mode, which remained grayed-out as if I was doing SVD sampling. Until, that is, I went on a hunt for all of my sample stars and clicked off the blue boxes one by one. After the last one was turned off, my synthetic modeling options suddenly appeared.
This may have been discussed before in theory, but this was the first time I ran into the issue in practice - there does not seem to be a way to clear the samples. Re-running apod mask did not work...those little blue boxes have staying power! I also tried to trick it by using a blank txt file for Load PSF's, but ST just laughed at me. I suppose the quickest way to switch from sampling to synthetic is to just cancel out of SVD and enter again? At least if one wants to choose from the array of modeling options.
Anyway, my other thought was more of a description matter, though it's possible I'm just not thinking about it correctly. SVD with a single sample is described to be like 1.7 deconvolution. Probably setting aside that the masking works very differently, of course. But anyway, what particular base "model" is being used?, as of course there are no choices (Moffat and so on) as there are in 1.7, which can in fact lead to quite differing results. And as noted above, if even one sample is chosen, the synthetic side locks to Circle of Confusion. If one were to then engage that by turning on synthetic iterations, I am guessing that would be akin to 1.7 with a secondary PSF selected?
Not that it really matters as it works great, just curiosity really.
As a side note, I also tried the planetary button for the heck of it, as I know that clears the mask. Again, samples survive that too. They are like the undead! 
Planetary also makes other changes, which can only be reset manually - there is no undo or reset back to non-planetary. So once again, really the only way I have found so far to escape from either dilemma semi-expediently is to leave SVD completely back to the main menu and then go back in fully anew to start from scratch.
)
I am full of stuff like this. For example my current quandary is just what does the "%" value for Airy Disk in SS actually mean? (I know that I generally decrease the parameter for wider field).