L2ARC only does metadata out of the box. You have to tell it to do data & metadata. Plus for everything in L2ARC there has to be a memory page for it. So for that reason it’s better to max out your system memory before doing L2ARC.
It’s also not a cache in the way that LVMCACHE and BCACHE are.
At least that’s my understanding from having used it on storage servers and reading the documentation.
They would need to learn the meaning of consent first...