Ask HN: LinkedIn Endorsement

Here's my story. I worked with a startup on its early stage 2 years ago and did pretty good. I was laid off after a year since they want an in-house developer but during my last day, the CTO/Co-founder praised me for my excellent work and thanked me for my work. He also told me that if I needed a LinkedIn endorsement, he'll write me one. At that time I didn't have a LinkedIn account.

Fast forward today, I'm asking him the recommendation he told me before. If you're an employer/manager, is this rude to ask?