Why wear triangle elastics on upper 1st premolar and bottom premolars as opposed to upper canine and lower canine and premolar?

I am in month 19 of braces & I was just given triangle elastics and I was told to wear them on my upper 1st premolar & connect them to my bottom 1st & 2nd premolars. I have noticed by researching online that the typical way to wear triangle elastics is to wear them on the upper canine and connect them to the lower canine and premolar. Why do you suppose I'm being told to wear them this way and what is the difference?

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