To go back to your car analogy, isn't an RPi like a 25 year old econo beater? I always took homelab to refer to a home datacenter; I always assumed (possibly incorrectly) that the origin of the name was due to the analogy of someone who sets up something like a chemistry lab in their garage.

I think of it as the computational equivalent to a home machine shop. If you don't have some heavy duty equipment can you really claim you have your own shop setup?