Have concrete inground pool being renovated. My concrete guy said since I'm doing cantilever coping they need to do pour before pool guy puts liner in. Something about forms need to attach to liner track. Is this the case? or is it just easier for him? Is it possible to install liner and attach forms to top of pool wall? worried about pouring deck before pool is run/checked for leaks. Maybe this is how its usually done. Any info would be greatly appreciated

Its easier for him. No reason you can't pour it later. Around here, a lot of times the deck and coping (cantalever included) don't get poured for 6 months.

My recent build was concrete coping first. They used Stegmeir forms and they did attach to liner track. It was reverse of a normal vinyl pool install.

I would wait. Doing the decking first means you don't have to worry about stuff happening to the new liner. For example dropped tools, a splash of wet cement etc. It would be a bigger deal if they had to remove the old decking because then you would definitely have chips and chunks of concrete in the pool. bk is right, but if you can do it in the order the pb wants it just makes things a little easier.