The long travel derailleur almost touches the ground.
actually the cage length is for chain slack take-up, reduce the amount of chain length difference
with just one chainring, and a 9-26t cassette you can use a short cage RD..
(Big+big )-(small+Small) is the slack difference in tooth counts.
[and if a 2nd chainring at all , keep the difference small.. say a 48-56..]
(non birdy owner)