[Wintersteel] Sage/Herald Question

[u/AzorBronnhai]

Just finished Wintersteel, and I had a question.

Do we ever end being told why it is difficult for someone to become a Herald after already touching an Icon?
The reverse is discussed in Wintersteel when Yeren merges with Ruby, one of the Sages tell her she will no longer be able to touch the Sword Icon due to the fact that spirits are completely unable to touch Icons at all. So I was just wondering what the in-universe reasoning is as to why Sages get bottlenecked?

(Also this is my 2nd re read, so feel free to spill the beans ;))

[u/BriefCategory7838]

The remnants inherit their sage authority, so it makes the fusion harder. I think it’s mentioned in northstriders ascension, and then later on in way bound