Maybe we need separate thread to discuss buybacks.
Please note that promoters are trying to distribute the cash on balance sheet to shareholders including themselves. At the same time they want to pay as little tax as possible.
The difference between buybacks you mention above and this one is, promoters are participating in this buyback i.e. 4% of their shares will also be bought and extinguished by the company. Because of this, it is not a true buyback as you are mentioning above.
e.g. Imagine that, there are 100 shares of company, 50 are owned by promoters and rest 50 are owned by 5 shareholders 10 each. Now company decided to do 10% buyback and promoters will participate. In this case, there will only be 90 shares of the company after buyback, 45 to promoters and 9 each for rest of the 5 investors. Please note that, if everybody participates - their share of ownership does not change in the company e.g. promoters still own 50% of the company. In case of buybacks you are mentioning, promoter’s ownership will go up.
If someone does not participate, yes his ownership of the company will go down.
So again, this is not a buyback at all but a dividend payment in my view. Also when we are looking for multi-bagger gains in stock market, I don’t think we need to spend a lot of energy on 2% here, 5% there.