IMO, what you heard is true to a certain extent.

Border Collies are often misunderstood because they have not-exactly-natural behaviors. For example, their stalking movement and hard eyes can confuse and set off other dogs. From what I've read and heard from other BC owners, attacks from other dogs due to body miscommunication are not uncommon.

However, you will notice that it is BODY miscommunication, not a simple matter of prick and drop ears. Dogs communicate with their entire body. A dog will not focus in on a Doberman's cropped ears and perceive it to be a threat. A dog will look at where the weight is being held, the base of the tail, the tenseness of the muscles, the facial muscles, the hardness of the eyes, etc. It's not a matter of pick/drop ears or tail/no tail. It's much more intricate than that.

And dogs certainly can and do pick and choose their own breed out from a pack. I guarantee you: If you take two retired racing greyhounds and stick them on opposite sides of a dog park, wait 5 minutes, and those two greys will become inseparable. I absolutely guarantee it. Greys "know" other greys. Could it be due to their upbringing at racing farms? Possibly. But they definitely recognize their own breed.