For a layman, what does certification mean? Certified for what?
And while there are countless single engine jet planes and many small business jets without lavatory, there indeed aren’t many (“jet” engine && single engine && business jet) designs, let alone civilian type certified models.
Usually when someone says a plane has received its certification they mean it’s ‘airworthiness certification’, so the final approval by the FAA.
Usually, EASA and FAA cross certify, making it easier to get one if you have the other already. Fascinating stuff, aerospace certification.