When they start with the old style there is an overload of concepts where the teacher just have to say "ignore all this", which is not ideal. With new style they grasp fewer concepts at first.

I'm not truly convinced this is such a big deal, but I lived through my university switching from Pascal to Java in the first programming class, and I can confirm people did get much more confused during the first few classes (to be fair they got way less confused later not having to deal with pointers tho).