Usually they see through areas in between the eyes.

Yep. On some of the OG show's stunt helmets the "tears" are clear enough that you can see the suit actor's eyes behind them.

Yeah, cause with Riderman my brain processes it like it is a super sentai helmet as I focus automatically on the tear marks as the visor of the helmet and the red compound eyes are for show. :lolol

Is this your interpretation or is there an actual source for this?

I thought this was somewhat widely known, especially among Showa fans. Though exact information is hard to track down, there is this https://mobile.twitter.com/Cross_Ult...45723855065090

Ishinomori was a big fan of this idea of reluctant fighting. It's not hard to see that in his authored works, so the connection does add up.

Random tangent, but there are also the surgical scar marks that Hongo had in the manga version of Kamen Rider which was later referenced in W every time when Shotaro transforms into Double they appear around his eyes. Not the exact design per se, but it is a nod to that.

Wataru from Kiva also had those line on his face when he transform too as well.

And Vulcan! Pretty sure there’s a couple more examples.

I don't know why it took me so long to realize this, but the red/green/yellow kiramagers have dashed lines across their chests to represent road marks, and blue/pink have the single line to represent contrails.

Yep. Subtle but clever.
On a side note, just remembered Kazuya Nakai is probably one of the few voice actors who is a rider and a ranger having played the role of Eiki and Garu/Ohkami Blue.