Our confusion came from the fact that existing tail-f packages use hyphens, so one would argue that our development of the packages (Cisco certified) sits on edge of what could lead to some unexpected behavior in the java code but could be prevented by omitting it in the name.
I looked at some internal engineering pages where developers use hyphens for custom services and this warning is also present in the output, but there’s no word about it; they just disregard it and continue with service creation examples. On the other hand, I found some SR where hyphen led to issue with the deployment of the service and also received a feedback from one of our SE colleagues from US reporting issues with it and Python interpreter, which led him to rewrite everything eventually.
I did suggest my client to leave it out for now - we’re in POC anyways, but they would like to have some consistency for future development, that’s why I asked this question in the first place. It would be good to have some official statement for it somewhere in the documentation (where we currently specify ‘package-name’ as a valid example), but I guess we’ll have to stick with warning received from the NSO which turned out to be true in some cases and leave it out for now.