Your placement of Base Saiyans, Kaioshin, Piccolo.

[SSJ2]

As for me, I go by what the manga says. My personal logic is meaningless when there are statements in the manga to go by.

 

[GSM123]

Goku expected Oob to already be an experienced warrior with knowledge and control over Ki (As he told Vegeta that Oob was "suppressing his power" when he couldn't even use it) and even seemed to doubt Oob upon meeting him, so his expectantions weren't 100% fulfilled.

Goku's mostly refering to how Oob was indeed Boo's reincarnation, as shown by the power bursts he'd just pull off. He even reckons he still needs training, indicating he can't access all of his power just yet.
Chapter: 519 (DBZ 325), P12.2-5
Context: Oob is surprised by Goku’s Bukujutsu
Goku: “Oh, I see. You still don’t even know how to fly, huh? …I guess there ain’t no helping it. You haven’t had no teacher, and you probably never even considered things like that. Sorry I bad-mouthed you before. Please forgive me. I just wanted to know your true ability. You’re exactly the person I thought you were. As amazin’ as I expected. But you don’t know how to use your power. This is the first time you’ve fought like this, right? I've got it! From now on I'll live with you at your house and teach you!”

Much like Kid Gohan, he could only access a portion of his power rather than all of it, being barely enough to match Base Goku.

Also, there's a contradiction in what you're arguing. If Oob could already access Goku's full power and Goku is SSJ3 tier in base, then how can Goku still look forward to fighting Boo after all these years? After all, Oob would just be a fraction of Goku's power by that logic, and Goku didn't expect to train him. Or do you think Goku can no longer transform?

As for your point about “magically becoming stronger”.

Well, there's a problem with that logic...

Or, in Toriyama's own words:
The key words this time, “God of Destruction Beerus” and “Super Saiyan God”, were suggestions from the scriptwriter, but they were good ideas for presenting a crisis for the main characters, who had grown so strong that they’d reached a point where there was nothing higher.

As for me, I go by what the manga says. My personal logic is meaningless when there are statements in the manga to go by.

So do I, though. Whenever I'm basing something off my own interpretations rather than actual evidence I make a point of saying so. I also base myself on secondary evidence, such as guidebooks:

I'd also like to point out that's rather ironic when taking into account you argue Gohan was a SSJ1 vs Dabra (Something based more on personal interpretation than objective evidence), but that's for another thread.

 

[GSM123]

Icing on the cake:

In this last case, it's evidenced that Oob didn't just unleash all of his power at once, and rather gradually unlocked it throughout the fight.