Actually the theory and the reality not match always, and that's basically my point.
And in the summer of 2016, while some miners were disconnecting, I am almost certain that not all of them were mining on profit. And it's clearly not the only case. And if it has happened before, it can probably happen again.
Also, what do you mean by the increase in difficulty?
The increase in difficulty is an effect of the increase in reward, remember that last year at 10k we were doing 100 Exahash, now we're doing barely double with 5 times the reward, the consumption is barely keeping up with the price because of chip shortage that leads to both Bitmain and MicroBT get sold out even if customers are ready to pay triple the price.
I've got an insane deal buying 3 miners at just 2 and a half the price of last summer, if enough mienrs would be available at this moment you will see difficulty do another x2 in a month.
The relationship between increase of reward and increase of difficulty is not necessarily as you say. It's somewhat similar to "what was first, the chicken or the egg?".
With the current semiconductor shortage the situation is unnatural an indeed the difficulty doesn't rise as much as expected, but, on the other hand, isn't this yet another sign that the overall rule doesn't always work as expected?