Hi maimad and welcome to the Plumbing pageat at AskMeHelpDesk.com. You piggybacked on an a 5 year old dead thread. In the future, before you post, look in the upper left hand corner for the date.
He is sending you on a wild goose chase until the clock runs out.
I think the clock ran out 5 years ago.
However, you gave a great answer. This practice is called, "bedding the tub" and if the plastic or fiberglass tub isn't supported by wood , cement or mortar then there will be trouble on down the line. We bed all our tubs by puddling cement or mortar under the tub. Especially around the drain. Thanks for your input. Tom