I wouldn't draw any conclusion based on one persons bad experience with any product. Too many variables and in some cases 1000 times more folks have no issues with that product.
Years ago before rubber roof material most rv trailers came with mill finish aluminum roof material like my '84 26' fifth wheel rv trailer. Those old mill finish roofs were hot in the sun. The material came in huge rolls and was oily. This was before white aluminum material became available.
Not much in roof coatings was available back then other than Cool Seal White elastomeric. I applied 3 coats per instructions over the mill finish roof. WE kept the trailer 7 more years and no issues with it. The trailer was much cooler with the white roof. There were no leaks on the roof ...I just wanted a cooler camper and got it.
The oils on the roof material needed special attention for complete removal. I cycled the prep instruction three times. Heavy oils were used in the rolling and crimping mfg process.
Painting a vehicle or applying a roof coating takes special knowledge and mostly experience with prepping the job. The part I always hated.