I put out a request for bids to several local house painters and quite a few seemed high. One was for over $6000 for painting the exterior of the house with putty fill as necessary, paint included. It was for him and one other guy to do the work. I said, "it's going to take you guys quite a while to get this job done" and he told me that no, they could do it in 2 days. I don't know about you but $1500 a day per painter seems more than just a bit high. I went with someone else and they had several people there for several days working like crazy and did a great job. There are too many scammers.
Back to the article. You can add water to all latex based paints / thinner to oil based paint. The tinting base has absolutely nothing to do with it. Say you are working outside and throughout the day you have to add a little water to keep the same consistency. If somebody really tried to add 20% to 50% water they no longer would be painting they'd be performing a whitewash or pickle finish.