AI Riggers are a weird case-- Most of the AI rules in 5th Edition are very confusing, sometimes even being contradictory. If you want to play an AI, you'll need a healthy amount of houserules just to be playable.
Normally when a rigger jumps into a drone they use their meat body attributes for skill tests. But what should an AI use? Ignore using an RCC in case that matters.
An AI consults the Foundation Attributes table on page 110 of
Data Trails if they'd need a Physical attribute. While Jumped In to a drone, you probably could only be asked to use Reaction (other attributes would be the Drone's attributes), which is the character's Data Processing.
What the character's Data Processing is depends
where they are. The AI could be
in the drone, supplanting its Pilot program, in which case its Data Processing would be based on the Drone's Pilot/Device Rating. Or, the AI could be in
a different persona-device like an RCC, Cyberdeck, or Commlink, and then be using it to jump into a drone similar to how a metahuman does it. In this case, their Data Processing (and thus, Reaction) would be based off the persona-device's attribute.
They don't automatically use whatever device is their Home Device; it's entirely possible for the AI to have left their Home Device and moved into a drone to use it.
Which leads into the other problem, the blurb in Data Trails saying to use Depth in place of pilot rating. Again, this can be a penalty to the AI as everything else gets to use the firewall and data processing of the drones they jump into for initiative for example. Example depth 4 jumping into a drone with a pilot 6 for instance. So in this instance, the AI is now easier to hack, and slower then a rigger jumping into the same drone, regardless of anything else besides simply being an AI vs meatbag.
You're correct, but it's far, far more likely that the drones you buy will have a Pilot or 2-3, and you are an AI with a Depth of 4+, with the Designer quality (+1 to Pilot of your home device) and Optimizing Pilot, potentially resulting in impossibly-high Pilot ratings as your AI makes the device stronger than is normally possible.