I wouldn't dismiss your original thesis so quickly; I think it's still the best explanation. I don't think the reported frictions between the Great Scipio and Cn.C. Lentulus were enough to discard a close association, given both their previous administrative relationship and especially the fact that the later succeded the former as Censor.
In addition to the virtual monopoly of the patrician executive magistratures for those 15 years, TRS Broughton identified some of their plebeian counterparts as Scipionic proteges (eg, M. Acilius Glabrio, praetor for 196 BC and Consul for 191 BC).
T. Livius also assumed such interconelian cooperation during the consular elections of 192 BC (Ab Urbe Condita, Liber XXXV, cp. X):
" There were many strong candidates,.. But all men's eyes were turned to Quinctius (Flaminius) and Cornelius, for as they were both patricians they were competing for the same place and they each possessed strong recommendations, for each had covered himself with military glory. But it was the brothers of the two candidates who most of all made the contest such an exciting one, for they were the two most brilliant commanders of their day. Scipio (Africanus) had the more splendid reputation, but its very splendour exposed him all the more to jealousy... Moreover, the former (Africanus) had been continually before the public eye for nearly ten years, a circumstance which tends to diminish the reverence felt for great men as people become surfeited with their praises. .. By these arguments he (Quinctus) succeeded in beating his competitor, though his competitor was supported by his brother (cousin) Africanus, by the house of the Cornelii - it was a Cornelius (Merula) who was conducting the election - and by the splendid testimonial which the senate gave when they pronounced Africanus to be the best man among all the citizens and most worthy to receive the Mater Idaea on her arrival from Pessinus".
Now this was how the Senate was working those years.
Actually, the main support for your thesis would be negative; the virtual dissapearance of cornelian magistrates after the Asiatic judicial affaire and the subsequent decline of the Scipio brothers. In fact, the younger Scipios (Asiaticus & Nasica) were defeated as candidates for the Censorship, both in 189 BC & 184 BC, the last time by their sworn enemy MP Cato.