All curators have different criteria for using their votes to give out boosts when Ecency VP drops below 80%. For example, one can only boost posts published on Ecency. Another curator may give out boosts only to posts that have boosted under 300 Points. Another may only boost low rewarded posts. Another may only boost posts with over 200 word count. Or any combination of the above. There are no hard rules about what gets boosted. It's up to each curator. It is one more way that blockchain is decentralized. Curators are volunteers and independent, Ecency has some suggestions but ultimately curators freedom on their selections.