Completed with my ACL surgery.

Firstly all the meniscal injuries can't be identified on MRI. So there is a high chance for detecting meniscal injuries intraoperatively. Secondly the meniscal injuries in white zone rarely heals and your meniscal injury is irreparable according to surgeon, so he is left with no other option other than trimming it. There will be high chance for a meniscal injury to progress if it is not trimmed. And lastly your question does that make any difference? If you mean in positive sense yes, it arrests the progression of meniscal tear to a large extent. This is the main reason for any surgeon to trim meniscal tear. If you mean negative effects, yes again, it progresses cartilage wear but it is more after meniscal excision than meniscal trimming. So do good exercise and maintain fitness to retard untoward effects.