As long as there is no "landing distance procedure apply" , there shouldn't be a reason for you to apply a landing distance factor.
Additionaly ,(On A320 family ) In an engine failure , the PTU still supplies the remaining hydraulic system . So your hydraulic system is not downgraded , and your braking capability , and hydraulic systems users are not affected.
Now Imagine an engine failure along with an INOP PTU , there you go , you lost a hydraulic system . In that case you will have to apply a single landing distance factor corrsponding to the affected hydraulic system .
For the purpose of landing distance this is still not a multiple failure (engine failure +1 missing hydraulic !!) as engine failure does not affect landing distance.