Indeko Rune combination preview shows it will generate a Jewelry Glyph. Instead, an Armor Glyph is created. There is a different rune for Jewelry Glyphs with the prismatic trait.
Input Runes:
i have my main house (grand topal hideaway) listed in the housing tours, it has multiple target dummies, scribing altar, and grandmaster stations (in progress being filled out), as well as almost every antiquity furnishing on display to preview them
I tried this just now on PC-NA using those three runestones, and it made exactly what it said it would: a Truly Superb Glyph of Prismatic Recovery. I cannot put it on a piece of armor. I can put it on a piece of jewelry.
If it's repeatable on your end, I'd submit a /help ticket. It is clearly not a universal bug.