In my opinion I think the reason why source of income is very important in bitcoin investment is because bitcoin investment is not like that of shitcoin investment that you will just put your money and start waiting for the value to get hype No" hyping does not take place in bitcoin investment Rather the amount you invested will determine how the potential return will look like, so for you to have a reasonable portion you need a source of getting money so that you can be able to make a large portfolio by investing weekly or monthly, though most people can only investment in bulk and then allow it to compound, but anyone who is going with this approach will not be term as bitcoin investor.
Who then should be regarded as an investor if those that buy in bulk are not regarded as one, everyone has its own opinion of bitcoin investor or any investment but the general consensus of what am investor is someone or an entity that buys into something with the potential of making a profit from that asset, so the method of buying is not necessary to classify anyone as an investor. Moreover the person who buys in bulk is nothing different, the reasons for even doing a DCA is to get a best average price since the price fluctuates and most importantly to actually encourage small income earners to also invest and not thing they need large amount first to invest.
Those investors doing DCA usually will have an average buy price which is much lower than a bulk buyer and the bulk buyer can also have a better entry price that will be better than any DCA buy. The only people not regarded as investors are traders, they buy and sell in a day or week or even monthly, this are not regarded as investors in my opinion