He's right about Einstein: he was really a very great physicist, and general relativity was his. People who want you to think it wasn't often have nasty hidden agendas sadly. Einstein was also very human: when you read what he wrote you really get a feeling for how he thought and that, if only you were a little bit smarter, you could have seen the same thing. Of course 'a little bit' turns out to be 'quite a lot'. Dirac, say, isn't like that: he was really strange. But I don't think it's the case that there is Einstein and Newton on their own and then there are a large group of people collaborating: Einstein certainly worked extremely collaboratively with a lot of people. This is, sadly, one of the things that gives the detractors a foothold, so I'll say it again: GR was his discovery. Having learned, say, differential geometry from Grossman does not mean GR is not his, because it is. So he's both this towering figure and a member of a group of people who were all talking to each other. I don't know so much about Newton but I'd suspect the same. I think the reason he seems so secretive to us is that he was working in a world where people would absolutely steal your ideas and take credit for them if they could and that causes people to be very secretive. Einstein wasn't: once he'd published the 1915 papers nobody was stealing it from him. (I was going to include a link to the field equations paper: it says something quite bad about the internet that the link I had (to the publishing arm of a major university) seems to have rotted in a decade.)