Therefore, does the recent increase in the number of bitcoins held by whales indicate that the market may have bottomed?
Most likely so, the whales have settled for the low price and now they've started to but again, so we should expect rises in price soon, I suppose.
This is also confirmed by the trading volume dynamics. On your graph in can be seen how the amount held by whales decreases gradually from Feb till May 2021.
At the same time, if we look at the trading volume for the same period we can see an increase.

The increase, however, isn't gradual and contains more spikes, suggesting that the whales sold BTC in large amounts over a short period of time.
If the whales will continuously keep on holding large amount of stock in crypto, the market will surely not progress. As long as they are holding it, no large amount of selling or buying will circulate in the market making the coins kept on a stable price range. Nevertheless, sooner or later they will do something that will affect the market bigtime, for now, we should learn how to play their game and try and find ways on how we can still take advantage of it amidst what they are doing. Let's hope the whales will have the heart to help small time crypto enthusiasts to becomes successful too in the future.
On the other hand, if whales held Bitcoins long enough this would decrease the available supply of coins and, thus, increase the demand, which means that the price would go up.