Before Groovy was Beanshell, which was Groovy's inspiration. And of course Groovy's creator, James Strachan, did say if he'd known about Scala at the time, he'd never have created Groovy. And Groovy's quite weighty itself, have you seen its Antlr grammar file?
So? He's talking embedding a small scripting language into a JVM project. Groovy fits the bill, Scala doesn't.
Groovy is not small, it's huge... and sloooooooooow.