there isn't any spare capacity and the Saudi pipeline is designed for a specific API gravity of Saudi light crude and crude with a higher or lower API gravity from other fields will not flow. Of course, transporting the crude by road to a Red Sea terminal is possible but you can't achieve enough throughput for it to be practical. Also the Saudi pipeline is a point-to-point system and cannot be side loaded with crude from another field.
So I think we're getting confused by technical vs financial and so on.
On spare capacity, it’s more of a bandwidth issue than a hard zero. The East-West pipeline is spec’d for about 5 million bpd and can surge to 7 million. Since they recently pushed around 3.8 to 4 million bpd out of the Red Sea port of Yanbu, there is definitely
some headroom. The real issue is that Hormuz handles roughly 20 million bpd.
Also, a pipeline doesn’t just brick itself because you introduce a different API gravity. You do have to manage complex blending, adjust pump station pressure, and handle batch contamination, but it’s an engineering and logistics workflow, not a law of physics.
As for it being a point to point system that can't be side-loaded, that is just how it was architected for Saudi’s internal supply chain. You absolutely can build cross border feeder lines, metering, and injection nodes. The real barrier is that doing so requires a massive, multibillion$ infrastructure sprint and years of political alignment.
So yes, the Saudi system can’t bail out the entire Gulf tomorrow, but it’s because of massive hardware and scale limitations that cannot be solved in a short timeframe, not because the pipes are magically allergic to foreign oil.