I think you're right here, smart investors will be averaging in between this range. Some will go all in around $20K, which may or may not work out in the short-term, even in the long-term it'll likely still be considered a good buying price. For example based on the graph you posted, we are at the equivalent of $6K in 2018 or $300 in 2015 based on bear market draw-down, where previously investors began accumulating again.
I personally remember returning profit into the market around $6.5K in 2018. While in the short-term price dropped in half, in the long-term, it was a good average price during that bear market. Because ultimately, no-one really knows if we will definitively go lower from here, and if we don't, there will be many that will wish they had already began accumulating at this level (in order to average in at a higher price if necessary).
Also to note, we are at the April 2013 equivalent lows. While the correction has been significantly longer than back then, arguably it has been as aggressive. I imagine many people back then would have assumed Bitcoin would of dropped to $10-$30 after such a parabolic move, but instead, for whatever reason, it made a low around $65 before continuing up to $1200.
Therefore, it is most reasonable to buy in parts, by the ladder method. Lowering the cost of your bitcoins, if suddenly the market drops even lower after your purchases. As a result, if, for example, you buy a portion at 20,000, a portion at 18,000, a portion at 16,000, a portion at 14,000, a portion at 12,000, and a portion at 10,000, then when calculating the average price, it turns out that you bought bitcoins at 15,000. Not the lowest value, but close to the bottom and most importantly, getting such an entry price is much more realistic than trying to buy everything at once with one lot at the maximum bottom.
While I agree that DCA in a dip is one of the best strategies, it's worth remembering it only works in long-term up trends, as is the case with all DCA in all assets. Below $8.3K for example, the average price of Bitcoin since 2010, this becomes debatable if Bitcoin is still in a long-term uptrend, as DCA effectively fails in the short-term. This is why there will be others who will wait for a confirmation of a low, or least a high probability that a low has been reached, as if worse case scenario Bitcoin goes much lower than most people expect is possible, they will be in a position to BTC at much lower prices, at a much later date.
Hence, the only issue with averaging between $10K and $20K, is assuming $10K will be the low. As if it's not, a $15K average won't seem like a great price if a longer-term bear market begins. I'm not even suggesting this is a likelihood right now, but only outlining that it remains a possibility (as it has always been for a decade now), but more that there will be investors who will remain on the sidelines because they'd much prefer to buy Bitcoin 20% up from the lows, even 50% or 100%, if there is a much better confirmation of a trend reversal - knowing that they could still end up buying below $15K (even if unlikely).
In reality, a multi-decade averaging plan should include buying Bitcoin from $20K to $1, as opposed to limiting to a level that seems likely for a low.