Yeah, sure the more problematic portfolios would have been the ones who made decently large BTC purchases towards the top of the BTC price range, and then his subsequent DCAs at lower prices were not enough to overcome the earlier lump sum buys at higher prices, so there surely can be some BTC portfolios that might take a while to get back into profits, even after several years of ongoing BTC buying.
On a subjective viewpoint to me it doesn't seem that problematic as others may be projecting. Due to market uncertainty we should be flexible with our timing plans while accumulating our portfolios be it for a long term or short term accumulation plans.
Having bought a lump sum at a higher price, what the investor needs to do is to adjust his plan giving it more time and if possible he/she can accumulate more BTC while patiently waiting within the adjustment period. You don't lose in BTC DCAing if only you can be patient with the market because it will surely take you back to profit. The only time anyone loses is when they panic sell out of FUD or impatient.