I have hesitated to jump in here because this is such a complicated area as we discovered a few years back when it was explored extensively. We can go round and round in circles, and the more you look at it the more complicated it gets, with so many "what-ifs) and scenarios. Perhaps we make it too complicated?
One point I would like to make is that the Term "SV/PROG" doesn't feature in the de Villiers numbering system at all - the MALE head of a tree there is not given a title/suffix/prefix - but the implied designator is A as the next generation is B. A isn't necessarily the first person to arrive in the country - it is the earliest known researched person in that table, just as in other tables such as Burke's.
Perhaps the time has come to make changes to what we understand or wish the current male "SV/PROG" to mean. There doesn't seem to be a single term that bilingually expresses that that person is the first person to head a family or branch of family of a particular name in South Africa - besides which changing it now would be impossible. Yes - sadly for some - this is/has been based on the male generated line of descent - with the mother acknowledged - differentiating between whether she was the first of her family in SA or of an established family.
The big issue seems to lie in the interpretation of what a Stamvader is - and whether stamvader actually means Progenitor - the definition of which is “an ancestor or parent"; the originator of an artistic, political or intellectual movement. Progeny = offspring or origin. My school “woordeboek” says simply that “Stamvader is an ancestor. A Stamverwant is a kinsman.
The literal break down of "stamvader" (stam and vader suggests the father of a line/branch. So if agreement can be reached that Stamvader and Progenitor mean exactly the same thing in this context - the Male person that starts a family in South Africa - then that is a good starting point.
Whether the line extends beyond the children he or she is father of is neither here nor there (there is no mention of the sex in the progenitor definition, but vader in SV obviously being male) - they are the Prog of A FAMILY, regardless of whether they are daughters or sons.
So that is for me a starting point. Do we designate a different suffix for a man who has only daughters - if so what? Perhaps if it can be accepted that the two words mean the same in this context, perhaps a man who doesn't have male descendants can be simply bracketed?
Male descendents - SV/PROG
Only female descendants (SV/PROG) or [SV/PROG]
Re-naming the numbers of profiles involved is just too big a task to ask - but identifying those who had only daughters would be much easier as there were obviously fewer.
In conclusion I don't think you can strip a person of the SV/PROG title just because he doesn't have male descendants, or because the male line comes to an end further down the line.
Food for thought