Aye. I fully agree, and I think that is something that completely goes under in most discussions and in guides. They are usually for the endgame, e.g. the goal and the "ideal" play, and many times take into account neither the low level play, learning curve or the other people in the group. E.g. when I wanted to check some SCH guides to maybe learn something new and improve, almost all of those I found were either old and outdated, or they only described max level play in a perfect group. There's much less out there for newer players learning the ropes, for which guides actually would seem more helpful - especially in a game like FF14, which is far less focused on only doing max level stuff in comparison to for example WoW.
I guess the most common and imo very misleading advice in healing guides is "it's ok to leave the group low, keep doing damage only slowly top it off when no AOE is coming". That tip completely disregards any player mistakes that might happen, e.g. moving out of the bad.
Anyone playing healer has to find his/her own sweet spot. I always try to maximize damage. But if I'm uncomfortable in a dungeon or trial, or see that there's too much damage or dodging stuff going on than I'm comfortable with, I can also do nothing for some seconds (break the ABC rule, which seems more or less every guide puts in the beginning) and just try to get a better overview of the fight, or overheal and throw around some shields. That being said, I'm still sometimes annoyed when some healers do trivial content (like MSQ roulette with good gear) and don't cast a single damage spell in the entire instance, but instead stand around for 95% of the time.