The filter I've dealt with the most is the standard Subaru 16546AA020 for my 2004 WRX. The factory one was made in Japan the "E" version I believe) with a oil media that had a red color. Ever since I've used OEM filters bought from dealers, although I had a stash of about 3 I bought for less than $10 each from a dealer in Washington selling them online. Also bought directly from dealers where the F version is now made in Mexico but otherwise identical to the ones that were made in the US.
Still - the OEM Subaru filter is a rectangular (reversible) panel and I've noticed that I could easily tell where the dirt was trapped. The vast majority of what it traps forms a crescent shape which is far heavier at the far edge of the pleats and the loading is deeper on the side where the air seems to flow. I look at a used filter and other than the edge I can reverse it and see very little filter loading on the other side of the pleats. I was thinking as it started loading up in the primary areas it should start loading along other parts of the filter, but it doesn't seem to do that. It even seemed somewhat caked since I hadn't changed the filter in a while, but still with most of the dirt right where it was loading. I thought maybe one could get away with reversing the filter, perhaps after brushing away some of the built up dirt. However, I've heard with oiled filters that often the loading helps improve filtering efficiency, although it may be at the expense of restriction.
In the past I changed the filter in my 1995 Integra GS-R, which had this funky cylindrical filter. However, it was dry and as far as I could tell the dirt seemed to load rather evenly around the entire filter. Looks similar on my wife's 2002 Civic LX with a dry panel filter with a thick polyester media and that seems to load up relatively evenly.
I don't remember exactly how it worked with the old cylindrical filters. I remember changing the round filters for a Chevy Lumina APV. They were lightly oiled paper. I believe it was a traditional design where the intake goes straight into the side of the filter and then through to the throttle body on the inside of the filter housing. That was what I remembered from my youth, with a round filter housing with an intake, along with a round cover that clamped down on the filter seal with a wing nut. I'm guessing that they tend to load up more on the media on the side of the intake?