On my 2018 Aspire the filler is usable to add water or chlorine/bleach.
In the picture shown it looks upside down. Also, it is mounted too low and should be above the top of the tank. ... if I interpret the picture correctly.
On the "foamy" water. I've found that to be a PEX thing. PEX is the type of pipe used for the water system. We had PEX installed in our home and had the same issue. When you first run the water it's foamy for maybe 60 seconds and then clears up. Apparently there are different kinds, or manufacturers, of PEX so your mileage may vary but for us Entegra owners it may be common (when new). It's not supposed to be a problem.
That said, I will sanitize my system, using the procedures outlined, and see if it helps the foaminess. It's not severe, but it is noticeable.
2018 - Entegra Aspire, NIRVC
2011 - Subaru Outback