I think you are almost talking same thing as diversifying if I am not mistaken and JJG and some others has address this issue that one should not thinking of diversifying until they have gotten to an overaccumulation stage because when you say other investment asset you are indirectly talking of other investment aside Bitcoin investment which can still sometimes distract one from there main investment ( Bitcoin investment).
I don't think it is even advisable to use other investment asset as a means of back up. Someone who is ready to invest in Bitcoin will always ensure to have a good discretionary, back and emergency funds the back and emergency funds are used for unforseen circumstances that may arise and so using other investment asset as a back up funds is not really a good strategy per say.
I agree with you, in the early stages of investment, we should never consider diversifying our investments. Rather, it would be better for you to focus on how you can take your Bitcoin investment forward and how you can strengthen your defenses. We should not confuse ourselves at the beginning and should not be busy with other investments. Because in this way you will only confuse yourself and move towards wrong decisions and the possibility of taking wrong steps may also increase.
When you are a skilled investor and skilled in financial management, I think you can start diversifying your investments if you want. Because you are already skilled in investing and being skilled in investing will also increase your ability to make the right decisions. Even then you may be at the last moment of achieving your goal and your defenses will be strong. Basically, you are skilled and competent enough to diversify your investments. So then maybe it will be the right decision.