One last try
If the author of Darrians had only used the terms ships and warships then I would support your view that some of them could have been spaceships - SDBs, monitors or riders - without hesitation.
But the passage I have quoted clears up all ambiguity - it states no less than three times that the relic TL16 ships (including the warships and civilian vessels converted later to military use) are starships.
OK, now my last (I hope, but don't promise
) try, with the same paragraph you quoted (with a little humor, and taking wording to extremes, if you allow me to. So, please,
don't take anything here seriously as part of my thesis):
Thus, survivability and endurance can be inferred to be two of the characteristics that Darrian tech level 16 starships have.
So, only TL16
starships had those qualities, non-starships had neither survivality nor endurance.
Probably fewer than two dozen Darrian tech level 16 starships survive today. (...)
As said before, but no number of non-starships is given, so the hipotesys they had over a dozen Tenders with their riders (too bad they were not as durable, though) is plausible.
In addition, a small percentage of surviving Darrian tech level 16 starships were not originally of military design. At least four are reported to be merchant ships to which tech level 14 weaponry has been added. The implication is clear that tech level 16 ships have qualities that justify such a conversion, while such a conversion at tech level 15 or 14 would be inefficient at best.
See that even non-starships (as here it talks about ships only) also had those qualities, though is clear that the ones initially non-military are all starships, and so jump capable.
How do they know, if they are not as durable (and if your theory is right and there are none of them)? Anyone's guess...
Or I could try to press that this shows some non-starships were also so converted (or at least upgunned, for they must be military designed, as all non military where starships), as otherwhise it would have specified starships...
And now seriously:
We can see we reached different conclusions, both probably equally arguable depending on how do you read (and probably what modules you have, and here I guess you have advantage, as you told about some I don't, but you were kind enough as not to use this advantage, if they are indeed clearer).
In any case, I guess we at least agreed in that no very large ships would be there, due to the pre-Maghiz lack of immediate need for them, as Whipsnade so strongly (and quite rightly, IMHO) defended.