Time is sequential. Otherwise, sequential build numbers are kind of hard to orchestrate in a distributed architecture. Not impossible. But it introduces complexities if you have many build machines.

I don't think semver compatibility is that relevant/meaningful here. Normally I'd also want the branch name as part of the version tag. We do that with our docker containers. Adding the timestamp at the beginning is a good idea as it helps sort things by recency. I might copy that. The CI build id is nice, but I typically don't archive these anyway. All this concatenated gets a bit long.