... i didn't know you could get hydroiodic acid by reacting iodine with phosphoric acid!, but according to this document u can-
https://www.thevespiary.org/rhodium/Rhodium/chemistry/mmda.txt (https://www.thevespiary.org/rhodium/Rhodium/chemistry/mmda.txt)
cuz phosphoric acid is alot more available that red phosphorus!
Read again. The document proposes to generate HI and phosphoric acid from iodine and red P, so your assumption is way off.
oh... damn
well i went back and reread it and it still looks like it says that you can do it that way-
"For this you will need to generate HI. You can do this either by dripping
dH2O onto RP/I2, or phosphoric acid onto I2."
OK, then the error is in the main text. You can make 57% HI by distilling a mixture of dilute phosphoric acid and KI or NaI.