I would personally consider the apparent generous tuning of smn to be fair reparations for the absolute butchering of the job's gameplay and skill ceiling from Stormblood. And I say 'apparent' because many 3rd party tools are still recovering from the transition to 5.1.
Consider the fact that without aetherflow to allow for flexibility in trance activations, there is very little opportunistic play left in the toolkit. For the most part, you are just forced to use all your trances on cooldown over and over and just hope the parts of the fight they overlap are favourable to them. When a black mage is allowed to do things like bank xenoglossy in downtime and use it judiciously when the boss returns, their output increases relative to their full uptime tuning. In contrast, when a summoner is forced to use their trances inefficiently due to poor overlap with fight mechanics, their dps 'in practice' will fall below their dps in theory.
In the future, more fights may come that clash particularly badly with default trance timings. There are many examples in current fights already, and ultimate with its sheer mechanic density is sure to provide more examples. It's not a bad thing to give the job an extra bump to build in a small buffer, so that the job's intended output is preserved even in those situations. If agency was still in the hands of the player, I would be confident that summoners would have the ability to punch above their weight no matter their tuning. Alas, not all jobs are as well designed as black mage, so in lieu of well designed rotations I'm happy to accept some artificial propping up - it achieves the same result in the end.
I gotta say though, summoner players are truly noble, have you ever heard of someone calling for nerfs to their own job? I certainly didn't see any black mages sticking up for their fellow casters when summoners and red mages were down. Just a lot of gloating over their guaranteed raid spot. Now that the tables are turned they are back to whining that they might have to play a different job for progression - you know, the thing you do for maybe 2 or 3 weeks out of the entire year.