Even if newer, if it is 'not' a whit-ish color to reflect the heat and solar gain... then COAT it! 

Sure one could piece information together from various sources over time and work to fill in the blanks by posting questions here, but if one desires to break into the space in a relatively short time period, finding a private mentor or using a guru program are the viable alternatives.I do agree that guru training programs tend to sugar coat things to some degree, focusing more on successful scenarios and outcomes. 

Then use gel stain, first on the area, then on the very last coat lightly, with a nice brush, the whole side panel.  

I also pointed out with my GC. he fixed by applying an extra coat of water sealant on the backerboard

All that being said, unless it's really bad I'd do a coat of paint remodel and clawfoot tub shower conversion kit on a low-end rental. 

My painter simply brushed and vacuumed it and then put on at least two coats of paint.

I did have to grow a thicker skin,  though,  as not all tenants are of good will!  

@Duke Giordano I invested with PPR Note Co at the tail end of 2018 and this was my 2018 K1.

I don't sugar coat anything.OK Don't get me wrong.

You get the seller (usually a wholesaler) enthusiastically pushing a teardown on any investor who will listen to him, insisting that it's worth all kinds of money in the right hands, downplaying the renovation costs and time and pretending to all kinds of fixer knowledge by self-importantly throwing out things like, "You've just gotta skim coat that!"