In the end, it seems that amongst the most reasonable and prudent of planners, would not overly lump sum at the top, yet if they were to make such an error, then (absent some rare surprise/emergency exceptions) they should be more than ready, willing and/or able to continue buying BTC if the BTC price drops after the lump sum investment and especially if such dip lasts a long time and/or dips in considerably large kinds of ways. Personally, I don't give much of a pass or have a lot of sympathy for the lump summers who are not ready, willing and able to follow up with further BTC buys.. and if they have blown their whole wadd, then they are likely guilty of gambling rather than investing, which sure they are free to do what they like, but I am also free to not have much sympathy for such an approach to BTC.
Definitely overly lump summing without proper financial planning has lots of consequences on the investor both emotionally and financially like being left with little liquidity to attend to basic needs and in cases of emergencies because when the lump summing is overly done, then it is evident that a lot of emergency funds must have gone into the deal and these might be emotionally stressful, especially when the markets move sharply below the purchase price and most times the investor might not be able to contain the pressure leading to panic selling and immediate loss in investments.
Other times the shock from overinvesting in bitcoin at a point can shorten the longevity of your investment journey as an investor since recovery time would be taken off to gain your balance and there is no guarantee the investor would return to regular investment pattern anytime soon. Also, the less informed investor may be gathering funds to lumpsum again and miss out purchasing at periodic good prices that DCA presents and possibly may not even be able to gather the mighty funds as expected, therefore ending his investment journey as soon as he started.
Investing as much as you can contain and following up with DCA helps you cultivate a disciplined approach to investing and be able to buy periodically and accumulate good stashes of bitcoin in no distant time as long as you have started, you are consistent with it and have set an investment target, you would achieve it with time while your periodic investments places less financial, emotional and physical burden on you.