Building an investment portfolio takes time, and surely we might need to adapt our goals with changes in various aspects of our circumstances and/or even changes in our target asset versus other possible places that we might choose to put our value. There is no real right answer, even for any specific person since a guy may even assess his own particular circumstances badly (or wrongly) and need to make adjustments along the way.
With the 7 BTC example verus the 21 BTC goal versus the 35 BTC example, I was not necessarily wanting to comment on whether 7 BTC might already be enough, yet I was trying to frame it with a hypothetical framework in which each person had considered 21 BTC to be enough bitcoin right now (at this time in the market), yet 1 person was still way under that target (only around 33% to the target) and the other person was right around 66% above the target, and to flush out the example even further, I am not even presuming valuations of the BTC holdings based on BTC spot prices, but instead considering the 200WMA as a way to valuate holdings..
I find myself in pretty much that situation.
I bought about 5% of my overal portfolio in bitcoin in 2017. I was able to duplicate that stash with signature and other campaigns here. I realized about 20% of it in 2021 bull run (avg price about 55k)
In the end, I have about 40% of bitcoin now, and 60% of a diversified portfolio (about 40% in Brazil bonds, but I feel safe).
I won't be able to accumulate much more bitcoin. Maybe I can buy some more in the crypto winter if the price goes below 50k (which may not happen), but even at $50k it would be very hard to buy one whole bitcoin ( I don't know if I need to add that risk)
In regards to diversification, it may well be questionable the extent to which MSTR represents diversification, since generally the idea of diversification would be outside of the same sector, and surely, I don't have any problem of splitting up some exposure, but the level of diversification would not really be very great between BTC and MSTR... even though MSTR seems to leverage someone what BTC's already existing volatility.
Maybe in the end, I hope will achieve my FIRE status with just my little btc stash. If BTC price can maintain itself above 250k I will probably retire (I will need to sell some, to make a diversified and solid portfolio to leave my job. Maybe even a house).