I've had good luck with concrete floors by etching (or alternatively, grinding) the concrete to promote paint adhesion by giving the concrete more 'tooth' to grip the paint. You don't necessarily have to etch the concrete, but it's worth considering. Here is one company's take on it:
I laid the slab in September and painted it the next August, no problems.
Mine was floated, manufacturers said to put the first coat down with thinners, next coat full strength, I put three coats down, the only thing that’s gone through the paint in the past 2 years has been because of something I’ve done, eg. Dragging something metal and heavy over the surface, that’s my bad, not the paint.
A thinner could help in terms of penetration by the first coat. The pores of the surface of new concrete can be blocked with calcium, aggregate fines, etc., and etching can help open them up. And as you mentioned, it seems logical to me that a thinned first coat might penetrate and solidify any blocked pores better than a more viscous coat.
