I was also somehow not sure to include it, but consider the following points: 
1. It doesn't change the semantic of the build system whatsoever.
2. As @jpdeplaix pointed, the speed difference is significant (quite more than 1s, especially on a HDD, or worse: on an unplugged laptop with battery saving turned on, which is a relatively frequent situation for me).
3. I have big hopes that it's going to be used by default in Oasis sooner or later (and then I will remove it from the tutorial).
4. At this point of the tutorial, the invocation is no more magic than  `Plugins: META (0.4), DevFiles (0.4)` for a newcomer.
5. It's stable in practice.

I don't see any downside, except the fact that the name "Alpha" is slightly scary.