mining in the meantime will make a fortune...
I can guarantee you, no one would ever buy from Company A again, and there would be many returns.
Agreed. It's one thing to test out the hardware a bit here and there to make sure it meets specs, but if it turns out Company A was mining on the hardware to make some quick cash I'd be super pissed...mainly because they're now selling me a used product.
Even "testing ASICs a bit here and there" on the main net when product is not available to customers hurts existing GPU and FPGA miners - it directly takes away their profits under the pretense of "testing". There is testnet-in-a-box available, and any manufacturer testing on the main net is simply dishonest: it's not about testing, it's about taking away profits from miners.