Hello, thank you for getting in touch. This sounds very unusual and not something we have come across before. We germination test and trial all of our varieties and they grow true to type. Those weeds may have germinated naturally from your compost and certainly wouldn't be in our seeds packets. It's more likely that the carrot seeds haven't germinated for some reason. For carrot seeds, please see the following blog and video which may be of help. Carrots don't likely rich soil, they like to grow in poor quality soil with around 50% sand mixed in. High quality compost can affect germination rates.
https://shegrowsveg.com/how-to-sow-and-grow-carrots/
https://youtu.be/0ocnNLIXyBk?si=zdyOKpoZ4sJ2pyGj
We wish you every success and hope that helps.