I'm 100% sure that everyone in Denmark is going to declare his crypto holdings to the authorities. There's no doubt about that. 
They will, Denmark has the highest tax revenue to GDP rates in the EU and the highest in the world, it's always funny to see people not realizing the difference in silliness to pay taxes when you know how those are used and how the government actually takes care of you, of course for someone living it a 3rd world country this take would be hilarious as there all the money gets lost or stolen but here in the north it's actually put to good use.
For example, people are happy to pay 25% tax on a new car for the first 10000 euros and 80% for the rest of the value and Denmark still has 10 times more cars per capita than Nigeria or India
That's true; it does; I didn't comprehend what it meant at first, but to me it seems it's overcomplicating things, as the nature of a large number of investments, including cryptocurrencies, is highly volatile. What's the point then? From my understanding, it's what you mentioned already; it's an intrusive process to keep track of each investor's holdings, closely monitoring them every year, ensuring that they have the full history of your investment portfolio when they're sold.
Quite the opposite!
You have the whole document here:
https://skm.dk/ministeriet/om-skatteministeriet/publikationer-fra-skattelovraadet/rapport-om-finansielle-kryptoaktiver
Quote
The Tax Council has considered three different taxation principles; a traditional realization principle, a net profit principle and an inventory principle. Overall, the challenges of a realization principle are that the calculation can be complex and difficult when there is a lot of trading. On the other hand, the calculation according to a storage principle is simpler, and it does not require that information about the trades be stored long after the acquisition. Particularly for the stock principle, however, it applies that a liquidity burden may arise when assets have not necessarily been realized to pay the tax with.
The Tax Council recommends that financial crypto-assets in future be covered by the same set of rules that
currently apply to financial contracts that are taxed on stock according to the rules in Chapter 6 of the Capital Gains Act
The Tax Council recommends that financial crypto-assets in future be covered by the same set of rules that
currently apply to financial contracts that are taxed on stock according to the rules in Chapter 6 of the Capital Gains Act