Stats 2B03 is a bit different since (according to the science academic advisors) people are expected tot take it in 3rd year for most programs, and it is only a 2nd year course due to the difficulty level. So tons of people from 3rd and 4th year will take it because that's when it's expected for them.
As for 1LT3, or any other course for that matter, just take it whenever it fits your schedule and don't worry about whether or not it's "weird", because nobody really cares. Besides, it's not like you'll be sitting in lecture wearing a giant sign saying that you're in 3rd year