Is it possible to fake GTmetrix or Page Insight scores?

Hi there,
So a few weeks ago I hired someone to improve my Page Insight and GTmetrix score. The score on GTmetrix came back all A's and nearly perfect. The Page Insights went from 8 to 80 on desktop. The actual speed when eyeballing myself, didn't really feel much different but I thought...hey the score is better?

A few days later after I tipped him for doing an amazing job. The score dropped back to where it was.
So it makes me wonder.....did I get duped?