No, you had an infinite number of choices on how to invest your money. Why single out buying BTC as the only other alternative to buying a miner?
What is said was:
If you had $7000 to invest in BTC
We're not comparing investing in BTC to other forms of investments, only investing in BTC via mining or directly.
I personally did buy BTC directly as well as buy a miner and I lost my shorts on the direct BTC investment. Sitting here today, I know I should have just held it but I sold for a loss of ~30%. When you say "you should have bought BTC instead of a miner", what you are really saying is "you should have bought BTC on the day you bought your miner and used your powers of prediction to delay selling it until today."
When you bought the miner you also invested in BTC that you would receive in a predicted future time period. You would have of course also predicted that the exchange rate would be the same or higher at that time if you decided to invest. The same is true when investing directly. You could have decided to hold those BTC until a certain period of time or many of the investment strategies that people employ. The fact is that you had the option to sell or hold which you don't when investing in a miner pre-order. So yes investing in a miner does help panic selling when you have no solid investment strategy but also prevents you from cashing out when there's a rally such as the time I was waiting for my Batch #2 Avalons and the rate hit $260. It works both ways and your decision to sell at a loss is not related to your BTC ROI on the miner.
I am not investing in BTC. I am investing in any way to make dollars. I have many investments. This one happens to have something to do with BTC but what it does is generate dollars.