I don't think standard Rattata has loot. Here's what makes me think this way.
I started to use covet on Meowth and Rattata during the day in Opal Ward.
-- I've gotten 2 or so quickclaws (that's at a the reduced spawn rate compared to ratatta)
-- Rattata has yielded no berries whatsoever. Despite me running into tons of rattata.
According to Bulba. US/UM A. Ratatta has carried pecha berries, while the standard rattata hasn't carried loot since HGSS.
~I also think A. Rattata doesn't spawn in Opal ward. (I've looked in all times Morn./Day/Night
Update:
I just did a 100~ encounters with Rattata in Opal ward and got 0 pecha berries.
Meowth on the other hand gave me 7 quick claws @ 60~ encounters
Will let you know if more held items are wrong. So far so good, I just tried Grimer and got black sludge.