The Synology NAS will complain if you try to create an array with unsupported drives but will likely let you continue at your own risk. I know this from personal experience as when I bought a NAS a couple of years ago I fell into the noob trap of buying 4 SMR drives as they were cheaper but also because they happened to be recommended by the guy who runs the "NAS Compares" youtube channel as a goof black friday deal, but failed to mention the potential drawbacks of SMR drives. You'd have thought that guy would have pointed this out, but for some reason he forgot. Being none the wiser I got them and set the thing up with them and got the warning whilst creating the array, but continued and let it set up.
It has been fine since, and reading up about SMR drives I know that my use case is on the lower end of the potential risks because I don't to a lot of daily writing, and I also have external back ups of everything. The main drawback apparently is is it ever came to the NAS rebuilding the array of one drive fails, it take much much longer to complete apparently. Anyway, I am actually now planning on replacing them with CMR drives, mostly because I am running out of space, and the drives taken out will become mre external back up.
In summary, yes I have put "non-compatible" drives in a Synology NAS, but I kind of wish I hadn't but also know that because I keep backups it's not such a big deal.