@ai6yr

As you wish!

Based on a bit of flabbergasted Google sleuthing, I've come up with the following TL;DR

Actually leaking oil (not drips, normal spray that's condensed, or other general messiness) from a...

Stihl, Husqvarna, echo, shindaiwa, or poulan pro - Problem.

Craftsman, poulan, Ryobi, or homelite - expected to varying degrees.

I will now explain.

@ai6yr

Some pertinent facts:

Most homeowner through farm and ranch (also called property owner depending on brand) bars are laminated sheets of metal.

The bar has a groove for the chain. That's obviously where we want the oil to stay.

Regardless of the mechanism, chainsaw oil reservoirs are positively pressured at least - on bigger saws a decent pump is used.

The chain is tightened on the bar by use of an adjustable stud which is in a hole of the bar.

@ai6yr
The 'trough' in the 1st attached photo is how the oil gets out of the reservoir.
Photo 2 shows the bar & chain as they're oriented while in use.
The black stud in pic2 is the tension stud. The large hole opposite it is there so the bar can be flipped and used in both directions.

This is when I first became confused.

How does the oil get into the groove where the chain sits? Something looked wrong so I grabbed an old backup bar for the firewood saw...

@ai6yr

Where the oil hole on the new bar?

@ai6yr
Remember how I said that the bars being laminated was pertinent?

Someone somewhere decided that cutting a slit in the center third of the lamination and making the adjustment stud do double duty was a great idea.

*Some* oil goes in, but exhibit A shows where most of it ends up.

Exhibit B shows the bar and chain attached... and a toothpick sitting all the way in the oil tube which leads to the reservoir.

@ai6yr
In addition to the Stihl bar I had in my hand, all the attached screenshots show that oil hole.

The oil hole does NOT go all the way through and thus there's nowhere for the oil to go when it's not running.

@ai6yr
Now I mentioned a bit back that my poulan p4018wt didn't leak.

And it turns out that in spite of lacking an oil hole and simply pumping oil into the center of the lamination, that model does so at an upward angle.

So the maximum oil spill is whatever's retained in the bar after use.

Considering I clean the bar before storage, I never would've had any to spill.