But also the cha affects the physical word for the spirit magic knowledge (increasing the number of spirit spells slots), because it's specified into the manual. And, in the same way, the chaosium errata corrige seems wanting count the pow of the fetch for everything, here https://wellofdaliath.chaosium.com/home/catalogue/publishers/chaosium/runequest-roleplaying-in-glorantha/cha4028-runequest-roleplaying-in-glorantha-qa-by-chapter/cha4028-runequest-roleplaying-in-glorantha-chapter-15-shamans/#ib-toc-anchor-16
Tell .."The fetch provides POW and magic points to the shaman. Its magic points are always accessible to the shaman, and its POW is nearly always added to that of the shaman’s (except for POW gain rolls)"
Of course, I'm not assuming that it's correct, but only that it looks like that in the rules 😉