I went back and found the scene that inspired this post! (Assume from here on out that I'm talking exclusively about CQL canon. If this exchange unfolds similarly in the novel--since Luo Qingyang isn't a Jin disciple in novel canon, it can't be identical--lmk!)
Wen Chao orders everyone to give up their swords. Jin Zixuan refuses. Wen Chao becomes angry, and it's Luo Qingyang has to diffuse the situation while fending off harassment from Wen Chao. She invokes the Jin clan and Wen clan's close ties, and then she turns to Jin Zixuan and says this:
Which is SUPER INTERESTING because it suggests a level of honest-to-god political savvy from Jin Guangshan!
Earlier in the series, when Jiang Fengmian arrives at Cloud Recesses after Wei Wuxian and Jin Zixuan's fight, Lan Qiren and Lan Xichen pull him aside to speak to him about the Wen clan's uptick in aggression. Lan Qiren mentions that they've already spoken to Nie Mingjue. Notably omitted from this discussion is Jin Guangshan--who arrived at Cloud Recesses at the same time and for the same reason Jiang Fengmian did, so excluding him is a deliberate choice rather than a matter of convenience. Given what Luo Qingyang says about the Wen clan and Jin clan being buddy-buddy, one can assume Jin Guangshan was left out of the loop because the other sect leaders didn't see him as a likely ally.
If the Jin heir has been summoned to Nightless City alongside everyone else--including two sects that have already been attacked outright--that sends the message to Jinlintai that the Jin clan isn't protected anymore. Their special status is on thin ice!
So Jin Guangshan does what Wen Ruohan tells him to do and instructs the Jin contingent to be on their best behavior for now, and for the greater good. This suggests that he knows full well that the situation is fucked and is waiting to see what is best for the sect. Whether that's playing nice to avoid Wen Ruohan's wrath or turning against the Wen in a big way remains to be seen, but he wants to keep his options open. (It also shows that he knows his son's personality; you don't have to explicitly say "keep your head down and behave while you're in a volatile political situation" to someone who is inclined to do that, and Jin Zixuan did just get hauled into Lan Qiren's office for punching a classmate after voicing displeasure with his high-profile arranged marriage.)
And sure, considering a continued alliance with the imperialist mass murder sect is... not great, morally. It's wholly self-serving. But nobody except the Lan and Nie had openly turned against the Wen at this point, and '"not getting super killed" is in the best interests of Lanling's inhabitants.
Plus, when an exhausted Jin Zixuan shows up with all the other disciples in tow with a story about how they were almost fed to a giant demon turtle, Jin Guangshan's switch immediately flips to going against the Wen. He sends reinforcements to help rescue Wei Wuxian and Lan Wangji and starts making military preparations, UNLIKE SOME OTHER SECT LEADERS I COULD MENTION. Some of it might be the personal insult of feeding his only valued son to a demon turtle, but it's also a smart move, because if the Wen clan is willing to blatantly harm an entire generation of upcoming sect leadership, all bets for alliance are off.
tl;dr I regrettably must give Jin Guangshan credit for doing a better job keeping his sect alive and prospering up through Sunshot. (Whether he's positioned it for long-term success later on is another story.)