If you're dumping warehoused parts for cheap onto the market then the primary, profit making production will cease, so you will be back to square one, with the market flooded with the "overproduced" parts, leading to stalled new manufacturing, leading to depleted warehoused parts.

That being said, the commenter you replied to is wrong. Yes, warehousing occasionally does lead to massive wastage. But warehousing in general is common even if it means things will be slightly more expensive. That's how the military is able to run equipment whose manufacturing ended decades ago. That's how manufacturing worked worldwide before JIT became widespread.

The reason it might appear warehousing doesn't work is because the news will report instances where it's gone wrong. They're not gonna report the significantly greater instances where things are working just fine, because that's not news.