To your point on "investors not being ignorant", have you followed the last 5 years of tesla stock valuation, and the constant signal that "this company P/E is disconnected from reality?" Meaning, despite no sales growth, consumer goodwill, etc. investors continued to dump money in? We see the reverse effect now, a slow massive draw down on stock value.

Anyway.

In the real world, a board(and also in particular the finance director) is more like to completely write off the unsold fleet, as it would allow both tax insulation and a more clean financial statement for auditing, investors. Mazda recently did this with the entire MX-30 program to signal to investors "this was actually intended from the beginning and allowed us EV research."

This happens in every single industry every day. Where Tesla to just mark the trucks down, that instantly signals to investors (note: not experts.) that there is a cash problem at the firm. There is nothing worse to signal as a public company.

While the current demand being priced in by some investors may be correct, wouldn't a lowering of the sale price still have to be reflected in TSLAs public disclosures and couldn't that still have an impact, both for investors and creditors?

Mind you, I tried my hand at shorting TSLA a long while (nearly a decade) back and learned, as many who undertook this, that rationality/EMH would likely never apply to their valuation. Made that (and then some) back thanks to Twitter though, so all is well, but not exactly coming at the idea of applying sensible concepts to TSLA neutrally.