UKC

Sean Bailey has made the 2nd ascent of Nathaniel Coleman's 'The Grand Illusion,' a Font 8C+ in Little Cottonwood Canyon, Utah. The steep roof is a low start to Chris Sharma's Euro Roof and packs in 25 moves without a rest.

Any other famous boulders where something like that happened?

The pinned comment on this post gives the history of the development of the boulder, sounds like a block was moved to open up the low start. This is a pretty common occurrence in boulders in talus fields. 
https://www.instagram.com/p/CHGfRRuDwsq/?igshid=ckekc2ugm8qo

The whole of Craig-y-Longridge? Although, that excavation was done for a housing development rather than to add sit starts.