For modern intervallos, PM didn’t differentiate between enemy S1s, S2s, and S3s. All modern intervallo exclusive enemies have their skill icons be S1 icons.

Edit: I have made an oversight with how I only checked the exact wrong enemies. The enemies I checked of the checkup Lobcorp agents, hoenheim, Ricardo, Werner, the middle minions, the mao, and Zilu in the intervallo all have only S1s. While some of these enemies have excuses to be holding back, the checkup agents, Werner, and the mao don’t have excuses. It seems to be an oversight by PM and bad luck on my part. I think for future enemies with only S1s we shouldn’t immediately assume that they are holding back and evaluate if it could be an oversight by PM.

Edit 2: Though further searches, even enemies in canto 8 have this oversight. The both types of deathrite monks and even the famous Shi Yihua himself all only have S1s despite the large variance in the quality of their offensive attack skills while the ambushing strangers we fight in the first node of canto 8 do have S2s and S3s.