This is accurate. The thing about mining is, there has been a once-in-a-lifetime boom in marginal profits with the advent of ASICs and the price increase combined. This gave the opportunity to be able to have to sell only a very small fraction of the mined coins to cover operating costs and amortize hardware costs. Should the marginal profits continuously decrease, "hoarding" miners have to dispatch of more coins than before to cover costs. Basically, there has been a negative supply shock (a withdraw of daily mined coins from the market) which is followed by the opposite, a positive supply shock.
It's definitely not usual to keep your mined goods as a business even if you have a big surplus, think of gold miners say. This happened because the mining industry was dominated by amateurs who are Bitcoin enthusiasts moreso than businessmen. Now, the space is getting much more professional, away from the few odd ASICs and onto big operations because of increased competitiveness.
I use
this graph as an indirect lagging measure of marginal mining profits, and as would be expected, it's been on a slow, steady decline ever since winter. I believe we hit a hashrate growth high in October at 3-4% daily growth that will never be seen again, and I think we can expect more predictable delivery of newly mined coins, and have been getting that for a while.
Just keep in mind that even though an important factor, it's only one of many regarding the demand and supply situation of Bitcoin. It gets more important when volumes are low.
