There’s usually a large enough sell off right before distribution that the price goes down, after which they buy it back again at a lower price. This way they avoid the dividend tax and also make a bit of capital gain at the same time. At least, that’s the calculation they make. The people on the other side of the sale are obviously making a different calculation.
I’m not trying to be argumentative but I could make the statement; ‘people always BUY their stocks right before dividends are distributed’. Given the irrefutable fact that for every seller there is a buyer. Many people are looking for yield (income), and in order to ‘avoid the dividend tax’ they must also ‘avoid the cash dividend’.
There is ‘a point’ if/when the stock price quickly recovers to its pre ex-dividend price, which can often happen. I think it’s unwise to make generalizations about something as unpredictable as the TAIEX.