LAMP, and other derivations on the theme, describe an environment in which lots of useful stuff can be put together. Saying one is a "LAMP expert" is ambiguous because that could mean several different things.
It could say the person knows how to install a LAMP environment on disparate OSes, it could mean it is the prefered environment of an architect who doesn't actually do much heavy lifting, it could mean the person can tune the environment to run really well with huge databases with lots of throughput. It could mean you're a one man shop that has had to configure and design the architecture, and code, and design/build the web pages (which sounds like your boat).
Like most buzz words, it's pretty hollow until you understand the exact memes and context that are intended.