Having never actually interacted with a mac from that era, are the grey and white stripes in the toolbar screenshots actually visible on the screen or are they an artifact of old screenshots on modern displays?
The striations were visible and the window panes that were unselected became translucent. A lot of themes of translucent glass/acrylic with a far-side texture.
The macs of the era had a matching theme to their design. Zoom into the front face of the Power Mac G4 "graphite" tower here:
The "pinstripes" were totally there, and celebrated by many. Note that they are slightly translucent, too, just like the pinstriped housings of the plastic Macs of that era.
They really didn't look bad, though. I think if you zoom the image larger it will give you a better impression of what they actually felt like.
They were definitely visible as part of the default theme, and you can see this replicated in the other desktop environment themes that mimic this, for e.g.: https://store.kde.org/p/1290811
They were toned down a lot by the time most consumers saw this (I don’t think any machine actually shipped with 10.1? They stuck with MacOS9 until 10.2, iirc…) and totally vanished soon after. But they were there, to start with.
I got an iBook in mid 2002 that shipped with 10.1 as the default OS (with Mac OS 9 as a dual boot option).
In hindsight, the pinstriping in the first couple of releases was a bit much, but sadly the buttons also got toned down at the same time as the pinstripes, and they've never looked as good since.
It's by design, I remember hearing that it would visually match the semi translucent plastic stripes of the original iMac frame, but those, while a bit similar, are vertical.
The macs of the era had a matching theme to their design. Zoom into the front face of the Power Mac G4 "graphite" tower here:
https://upload.wikimedia.org/wikipedia/commons/c/ce/Apple_G4...