Originally Posted by
pinniped
Yes, that's generally true - although when I flew through there in 2019 I noticed a sign that a couple specific flights did not have preclearance and you'd go through immigration after landing in the U.S. I don't know if there's a predictable pattern to it or not.
Preclearance has specific hours of operation. Most flights to the US leave in the morning to early afternoon. Sometimes airlines have flights that depart after preclearance closes.