Yes, it goes from 0% to 50% Latin, but then you've got yourself a Frankenstein mashup of Latin and German. If you're going to go Latin, go FULL Latin "Sanctified Spirit"
Like adding Latin prefixes/suffixes to German words, it's a bit clunky, bordering on the silly. It embiggens me to say that.
Holy is from Heileger (German) which goes well with Geist (spirit in German)
"Sanctified" wouldn't be right. But they're both English words, despite their roots. I don't consider "Holy" and "Spirit" to be a mixture of German and Latin/Romance but as two English words with their English meanings. If I wanted to go "full Latin," I'd just say
Spiritus Sanctus. It's not primarily due to etymology but due to connotations that "Ghost" has picked up over the decades and its use by Bible beaters.