It probably makes sense to keep the version explicit because every time there is s new active LTS version we always need to propagate changes to WordPress core and ensure that the deploy stack is aligned.

The other issue is that we always have to update this lts/* when we create branches for previous major WordPress releases.

@desrosj and @peterwilsoncc since you encounter some issues with it in the past, what do you think?

If we go this route we need to ensure that the documentation for contributors is updated so they are aware which version of Node.js is recommended. We could even send them to the updated file with the note that we aim for the active LTS version but in practice it can diverge. Example:
https://github.com/WordPress/gutenberg/blob/trunk/docs/contributors/code/getting-started-with-code-contribution.md#prerequisites

We landed #36744 that contains the same changes together with all necessary changes to the documentation.