I think Gil and others are right here in the fact that it appears to be a relatively outdated drawing (looks very much like a basic 60's/70's era 172 diagram)...the last shielded wire on alternator leads that I've seen is in 70's era planes - and we end up replacing them a lot. In fact, it's pretty difficult to get shielded wire in that size, most of us don't even stock it. I'd also probably suggest moving the wire size from AWG12 up to AWG10 or AWG8 in case you ever want to upgrade the alternator, you already have a larger wire (and price/weight differences are negligible). As mentioned, AWG12 is on the edge for carrying capacity. You'll also notice that the wire sizing is pretty much outdated as well if you're using modern equipment, modern LED lights, etc..
Also, we don't normally advocate running the fat wire all the way back to the panel anymore (no need). It's a noisy and heavy wire. Typically, run that big fat noisy wire from the Alt to the downstream side of the master relay, or the upstream side of the starter relay, then run a short (and usually smaller wire) from there to your main buss. It keeps the fat wire runs shorter, makes wiring simpler, and there is no need for that fat braker or ANL current limiter/fuse to be inside the cockpit. Also note that as shown in the diagram, that's an inefficient way to charge the battery (have the wire go all the way into the cockpit, across the main buss, through a jumper, then back out the firewall to the relay).
Just my 2 cents as usual.
Cheers,
Stein
CJ
