Buffy can be punched or kicked off her feet even in Season 7. I know that Caleb isn't a vampire, but the principal remains the same. It's physics. Apply enough forward force to an object, regardless of what it is, and it can be moved. If you don't believe it, kick a heavy metal bucket. You may hurt your foot, but you can move the bucket, even though it is stronger thn you are.
Anyhow, if you remember, Luke saying, "You're strong. I'm stronger," didn't keep Buffy from killing him eventually. That's why I've never bought into the "Buffy's stronger than all vampires" belief. She might be stronger than Angel, but he's not indicative of all vampires, necessarily, any more than Luke is. The best fighter isn't necessarily the strongest fighter, he's just the one who has the experience and skill to overcome his opponent's strength and skill. In Season 1, Buffy had the good sense to run from a confrontation with two or more vampires. It's doubtful that her strength increased so much that, by Season 7, she could readily slay multiple vampires at one time. She wasn't stronger, she was more experienced and better trained.
