Same problem for the vendors. If you are dealing with unpatched spares, so are they. Having worked for some of the big ones, I know that their supply chains struggle to get parts, too. Heck, IBM couldn't deliver a server internally in more than six months, imagine how hard it is to get support parts!
Shit like this just blows my mind.
Parts Bins, internal supplies for labs, and customer supply chains are all completely different (well IBM may have been a gong show). Dell and HPE staff can't just go grab something off the line, with Mfg you have to account for the costs and someone gets to pay (and often at a premium to prevent abuse) for those internal servers.
Parts Bins and stocking those are different, and supply chain for a OEM might actually be different in the us than EMEA.
At IBM< we were an external customer, even though we were inside IBM. We showed up just like any external enterprise customer. So their inability to support was universal.