If a pool exists where the rewards are shared among participants based on the amount of hash power that they each contribute to the pool, BUT each participant gets to run their own software to choose for themselves which transactions are included in the block (and builds those blocks themselves), would you call that solo mining? Most wouldn't.
I wouldn't call it a solo mining.
The scenario of the waitress in the restaurant seems that the miner is paid based on his hash power (working ability) just as an individual waitress. Let's assume the most hardworking waitress is thrown out of the restaurant to serve customers out of nothing, he will not make such money. The waitress is successful because a restaurant(pool) exists.
Let's see a scenario where there is a sea for fishing, and the target fish is dolphin. Individual fishers have small canoe that cannot penetrate the sea, then decided to join their canoes to build a big boat. Everyone of them climbs the boat for fishing and then one person catches the dolphin.
Is is correct to call him a solo fisher, because his hook caught the dolphin? Besides there would never be a scenario that two hooks from two fishers will catch the dolphin simultaneously.