@drachenfeles Good memory - took a little searching, but October last year was exactly right 
@alias_46913 the exact quote from the dev team was:
Twitch Comment: Question. Are the tree foundations lag/memory wise worse then the normal ones or better?
Robert: About the same. I’d also like to comment here and say that what REALLY lags the memory out is a massive amount of placeables, since placeables are not instanced but building pieces are. #pro-tip
This is from the 'Debaucheries of Derketo Comments and Questions section from this recap of a dev stream:
Developer Stream Recap: October 3rd, 2019
I don’t know if that will be enough to convince the server admin and other players (some people will stick to their beliefs no matter what), but hopefully it helps a bit