Marandy, 7 weeks is a long time, why hasn't the plumbing been completed? Waiting on someone to build a retaining wall is no reason not to finish the pool. Do they at least have a pump in the hole next to your pool? (or as Sevver points out, a well point, with a pump attached?)
Enough water behind the liner will cause the liner to 'float' (probably the 'squishy spots' you describe), this doesn't hurt the liner, but when it finally subsides, you will probably have wrinkles which can only be removed by draining the pool. It seems to me that this guy is 1) an idiot, 2) lazy or 3) has a crush on you and wants to extend his relationship with you. Some builders spread themselves too thin, too many jobs going at once, and some of the customers get 'lost' in the hustle - my best advice is to be the 'squeeky wheel' which receives the grease. Please keep us informed, we all want you to have the pool of your dreams - welcome to the forum!! know that you have thousands of people on your side for the pool to be perfect and are willing to help, in any way that we can - Waste