Doing an IPO this way, there's essentially no downside for devs investing in their own IPO. They wouldn't get any less BTC.. just wait until the last minute, and take whatever % they want , for free.. (since btc goes to their own wallet anyways).
They can't "invest" in their own IPO, transfering from one BTC address that you have to another BTC address that you also control you lose 0, hence they are taking 0 risk in "investing" in their own IPO.
All they are doing is diluting the premine share that the real investors are getting.
Lets say they get 100 BTC from real investors, each investor sent 1 BTC so everyone will get 1%, the dev keeps 0% of premine and 100 BTC from the investors.
Now the same investors send the same 100BTC but now the dev also "invests" 100BTC, now the real investors will only get 0.5% of the premine totaling 50% for them and 50% for the dev, this way the dev keeps 100BTC + 50% of the premine without really investing a dime.
Get it now?