You're right. What an irregular word.
finalize not named for the verb action they take to produce the result?
“Split every 3” also works in the past tense IMHO, but I feel like this is going to be a distraction.
I’m leaning back towards
maxLength: to reduce the amount of distraction, so we can focus on discussing the benefit to a Swift user, even though the bikeshedding will likely continue unabated.
Additional side thought:
intoGroupsOf doesn’t clearly communicate the semantic that a group may be less than the given amount in a way that
every: (forming a grammatical phrase) or
maxLength: (not forming one) do.