I could have written this exact post. I have heard the exact same rumours, and agree with everything in your post.
All the model 'girlfriends' of his are fakes/beards. None of them are ever over 25, they never go beyond dating, they always look the same, (blonde, blue eyed, pretty Victoria's Secret model types,) they always have the same pics taken (by the papparazzi,) of them 'kissing' and cycling together, and then we see newspaper articles where a 'source' says they're crazy about each other, she is getting interested in his environmental issues and supporting him in it etc etc, and his friends love her...
Then after a while (6-9 months) they start to be seen together less, she is getting a bit bored, and he is seen without her a lot, has his birthday and Christmas without her, and holidays with mates without her... And then a 'source' says she is getting tired of him and how it's not quite working anymore, then a few months down the line they finish. (Sometimes they just finish with no warning.) But they never live together, go to awards ceremonies or weddings or family stuff together, they never get engaged, they never get married.
I don't know how dumb Leo thinks his fans are. He is clearly gay (and yes Lukas Haas is very likely his long term partner.) I understand why he won't/hasn't 'come out.' As a pp said, it would have damaged his career so badly if he had come out 2 or 3 decades ago ... And maybe the ship has sailed now.....?
I wish he would stop dating 19 year olds when he's 50 though. I like him as a person/an actor/a celebrity, but find this side of him grim and abhorrent. At least get a beard who is over 30 Leo FFS!