Hi Melinda
Contradiction is a common thing to see and hear between different contractors and sales people. As true in any business some know what they are doing and some do not.
I can clear up one of the issues for you, all
engineered flooring is engineered flooring no matter if the locking edge of the boards are a Tongue and Groove or a Click lock type design.
The Click Loc design is relatively new type of locking system for engineered flooring which eliminates the need for any nails/staples or glue being used. Some manufacturer offer it some offer both types.
The Tongue and Groove system have been around for years and is manufactured to be nailed/stapled down to a wood subfloor or the groove of the boards glued to allow the engineered floor to
free float over any type of subfloor.
Hope this has helped clear up things and if you have any other questions please feel free to post them here.
Jeff Hosking