This only works if the investors believe enough in you to keep the funding going. I worked for a startup that decided to do the 'we'll work on a small project first to get our feet wet before working on the main idea'.
We did just that, put it out there, it didn't do so well, and the the board thought they weren't going to make their money back on the main idea and pulled the plug before we really got started on it.
If we had just worked on the big idea to begin with they wouldn't have pulled the plug anywhere near as quick, as there would be nothing in the market yet to underperform and give them a scare.
To be fair, those board members didn't have any knowledge of how a software-based startup works. They came from real estate and hospitality industries, and were openly and proudly ignorant about tech.