It does not really matter how execution ended up in the HV in the first place. The misprediction happens due to having a branch-to-register instruction.
He had to also mark the memory as inaccessible for code loads.
Which, honestly is kinda stupid. Because nobody asked the processor to start executing there. It just took it upon itself to try to start executing there, later decided that was a bad thing, and then borked itself.
People talk about how terrible x86 is, but honestly, one of the reasons that x86 won for decades was because of making things that programmers did that might be suboptimal still work, even if a bit slowly (misaligned data accesses, for example). ARM does that now for that specific case, but didn't before 2002.
So there's an implementation tradeoff for whether you decide to spend transistors to reduce the number of sharp edges on the tool. Obviously ARM just doesn't give a shit about this particular sharp edge.