The article you linked ahows a photograph of a skull and jawbone, said to be the giants, on display in a museum in Nevada.

There are records of another pair of mummies, one 8.5' and the other about 10' in that same lake area.

So I wouldn't say there's no proof.

It's possible these people, whoever they were, had a large genetic prevalence of gigantism amongst them. That might have been what isolated them in the first place and why they were so feared. They were different. It's doubtful there was a tribe of giants as we think of tribes. More than likely, it was a family living in exile or isolation due to persecution.

It would be interestinf to sona genetic test on those bones and see what their closest relation was.

There's a more modern equivalent to this theory. Check out the blue Fuegates of Kentucky.