Presumably this means they can remove an engine and use a fresh one for an Engine heavy race, and save the used one for another race that might be less engine heavy?
What i mean is, that once an engine has been used and removed, can it be re-used again and not necessarily at the next race, perhaps 2 or 3 races down the line?
Thats what I took it to mean yes, they basically have 8 engines, that must remain sealed so no rebuilds, but how they use those engines is completely free. It's a good change imo, one of the few that makes sense both in cost cutting terms and without ruining the sport by giving someone a 10 place grid penalty.