Nope, this does not mean that. Having your work featured by a publication is not required for boosting.

Our internal curation team is boosting stories all day every day, and most of these stories are not featured in publications. While most participants in the Boost Beta program are folks running publications, the stories they nominate for boost are not required to be in a publication -- theirs, or anyone else's.

Submitting your work to a publication that is participating in the Boost Beta program can increase your visibility, but ultimately it's just one of many ways that boosting happens.

The best way to make sure you're eligible for boosting is to ensure your story meets our distribution guidelines: https://help.medium.com/hc/en-us/articles/360006362473

(It's worth noting that a story being boostable/distributable isn't the same as a story being well-written. I'm a three-time published author, but literally NOTHING I have written on Medium meets the distribution standards. 🤣)