I'd have to agree, Megs have great customer service, and as a fan I have a shed full of their bulk products and many of their enthusiast range.
However, I do choose another product as yes, their trim detailer washes off after rain, hence the fact that after a soapy wash its gone.
Thats the reason I choose Z16, it stays on and doesn't streak, in fact has lasted 4 weeks & weekly washes and still looks good. I tried BW but not a fan. Cant remember why I gave it away now, I think it was too shiny for me even after paper towelling.