It isn't just about the number of attacks he took to go down. He was in a 10X worse condition even before he got injured—can't use haki, started off with a stab through the chest, still held his own against all 3 admirals. Meanwhile, Garp is almost done for the moment a YC1+ guy stepped in while fighting Kuzan. Even after all those drawbacks, WB put Akainu in the same state that Kuzan was in after fighting Garp.
Garp was the most active old legend with probably the best health history. Still looped much less impressive overall. Tbh, if it weren't for Garp's supposed rivalry with Roger, peeps wouldn't think twice before putting WB two levels above Garp. As a matter of fact, a lot people started questioning Garp's hype after the beehive fight.