Where a person heard a thing is irrelevant in this case. he is asking people here if they prefer center- or chain stay mounts for trailers. A I am sure when he asks for opinion he expects to get opinions. I am pretty sure he didn't think there was a legal case win which it was determined which was considered better.
I am pretty sure, since he is on the internet, that he expected snark and smart-mouthed responses.
In this case it was you, but it could have been me.
Funny, though, when you call me out for making just such posts.
To the OP: Most trailers seem to be side-mount, but I would prefer center-mount because of OCD. And any trailer like any load will change the way the bike handles, but you would adapt.
Problem with a cargo bike is that it Never would handle well. A normal bike without a trailer is a bike. A cargo bike is a truck, by comparison. The whole idea behind a trailer is augmenting a bike's utility ... it can be a bike, a bike with racks and panniers, or a bike hauling a trailer, all in one.