It was hardly a secret:

“The Royal Proclamation of 1763 was very unpopular with the colonists. For those living in the colonies, creating a boundary was not helpful because it did not address some of their biggest problems with the War. Colonial blood had been shed to fight the French and Indians, and many felt they had the right to go settle on the land that was won. In addition, the Royal Proclamation of 1763 did not account for American colonists who had already settled in the West.”

“Since the end of the War, colonial governments had started planning an expansion into the new western territory. In fact, this had become a big political issue among colonists”

https://www.ushistory.org/declaration/lessonplan/royalproc.html

"While the Proclamation Line generally failed to restrict the migration of individual settlers, it adversely impacted Virginia’s landed gentry through the mid-1760s. These men had been investing and speculating in land since the 1740s, preliminarily granting millions of acres of western territory to firms, such as the Ohio Company, for future sale. However, the French and Indian War and subsequent Indian treaties interrupted these land companies’ designs, during which time their preliminary grants lapsed. "

“These constraints particularly affected George Washington, who had dedicated much of his life to land speculation in an effort to achieve economic independence and distinction among Virginia’s privileged class.”

"Resentment for the British Empire and her interference in colonial affairs bonded Americans of varying socioeconomic backgrounds on a philosophical level. The ideological break with the mother country promulgated by the Proclamation Line of 1763, particularly for governmental leaders and Virginia’s landed gentry, served to push the colonies into rebellion in the following decade. "

https://www.mountvernon.org/library/digitalhistory/digital-encyclopedia/article/proclamation-line-of-1763/

"George Washington wrote to his agent in 1767 in support of illegally buying as much Native American land as possible. "

https://www.history.com/news/remembering-the-proclamation-of-1763