It certainly would be fraud [1] the question is, would it be illegal? Not all fraud is illegal, and not all illegal fraud is prosecuted as such (or at all). Even if it's not illegal, if the startup owner told the investor that they were growing rapidly and used these figures to show that, the investor could sue after the fact for civil fraud and the founder would have a hard time explaining why it shouldn't be. The only reason to grow headcount and increase burn rate to unsustainable levels and offset those expenses in the books right before an investor presentation would be to give the investor a misleading view of your company.

You'd be at the very least inviting a lawsuit... that is, if you got caught.

[1]

"Fraud involves misrepresenting facts for the specific purpose of gaining something that may not have been provided without the deception."

https://www.investopedia.com/terms/f/fraud.asp