Static compression ratio is calculated from swept volume and combustion chamber volume etc, etc... We come up with a value of 7.5:1 or 9.5:1, or whatever we want.
Camshaft timing - specifically when the intake valve closes is much more important.
Dynamic compression ratio is the important factor. Japanese engines ( or most modern designs) have variable intake camshaft timing - where the intake camshaft is advanced or retared wrt the crankshaft. This changes the dynamic compression ratio. Much higher static CR's are used when variable or late intake closing camshaft timing is used.
On a Cossie the camshaft position is not variable, and is not a late closing profile, therefore CR's of 7.5:1 and lower are used for high boost applications.
Honda engines with variable camshaft timing (phasing) and an efficient combustion chamber
can use a much higher compression ratio before detonation takes place.
One cannot make a blanket statement regarding compression ratio in a turbocharged engine. There are many more variables than just static compression ratio alone.

Just a thought from a Canadian ERST fan.

Cheers