1st, the Grading company's have incorrectly dated the 1949 LEAF BB cards as "1948". All 49 cards in the LEAF set's 1st series were issued in early Spring
of 1949.
The 1st series of the 1949 BOWMAN cards were available to us kids a few months after the LEAF's. And, of course the Jackie Robinson cards are in each
of these set's 1st series.
Anyhow, if you want to be a "purist" regarding Rookie cards, Jackie Robinson's first card was issued in the 1947 Bond Bread set (of 48 cards).
I hope this info helps. And yes, I'm old enough to have collected all 3 of these sets. I still have my original cards from when I was a kid in the late 1940's.
TED Z