. I got my endorsement in April 2022 and when they asked when I wanted to enter the UK in my stage 2 application, I filled Feb 2023. And that is exactly what was put on the vignette.
Everything went well. The only thing you will face is that your BRP might not be available at the post office that you chose when you enter the UK. You just need to contact the home office and they will deliver to your house at no cost.
Also your time starts reading from when you enter the UK