Different inks may suffer different reflective issues on different printers. If you are talking about one printer -- the epson 7600/9600 -- I could be very wrong. I suspect a truly bad rip or driver could affect metamerism. I stand corrected.
I use 3, 6 colour epsons. One with archival B/W, one w/ archival colour and one with dye colour, an 8/12 ink colorspan and a 6 colour HP designjet. I have 3 different rips (printer specific, ranging in cost from 2k to 9k) as well as manufacturer printer drivers, an untold variety of papers, fabrics and plastic print materials (all manufacter and ink specific).
The same printer/image using rip or not will suffer from metamerism on a variety of materials. Fabric and canvas being the only material that does not suffer from metamerism.
The dense areas, blacks, followed by dark blues are where I see metamerism on the prints I make as well as most uv/pigment inkjet output I have seen. Your experience may be different.
Finally, I don't mind metamerism that much. I took exception to your statements and as I said I stand corrected.