No, that’s not true. Dogs generally are less social as they age. The vast majority of dogs are ‘dog selective’, just like people are. As in they only like certain dogs and dislike others.

Very few dogs are actively hostile or actively friendly to ever dog, and often it’s due to their personality and training of the owner, than ‘socialization’. Proper socializing of a dog is not about other dogs so much as it is about introducing your dog to different environments and stimulus, of which other dogs are only one thing.

Not to mention many people ‘socialize’ their dogs poorly. I live next to a dog park and every couple of days some new dog owner dumps their 3 month old puppy into a crowd of dogs to ‘socialize’ it and shoves their face in their phone and chaos ensues. And they never come back.