"Proper" touch typing (I typed without looking before too, but not the "proper" way) is overrated and has proven to me less useful than the way I was used to.
Worse (IIRC), "proper" touch typing exists in a vacuum and has no context of the prior keypresses - rotating fingers or even switching hands at the boundary is going to lead to faster typing when you remove the artificial restrictions of "proper" typing.
BUT when you cannot touch type at all the notion of "proper" fingering provides a framework to work within and helps to form best practices that combat things like "press every key with index finger".
You'll see this in many skills and sports:
Beginner - no knowledge of the rules Intermediate - can apply the rules Expert - breaks the rules to achieve greater performance Master - creates new rules
Ultimately the best fingering for touch typing is the one which leads you to type the fastest and most accurate with the least amount of energy/effort. Achieving the optimal fingering as declared by someone else isn't really the goal.
I do this because I keep my hands angled a little bit inward, to avoid the awkward and un-ergonomic bend in my wrist. That is, if standard position is like this:
oo
/\
/ \
oo
/ \
/ \Hand angles and wrist position are somewhat glossed over if you only know "finger x presses key y"
If you think about violin and guitar - you learn how to play the same note from different hand positions so there is some (small) potential for this on the keyboard
Yeah, sometimes it helps to learn the rules before breaking them.