As I’ve said I’ve always heard the opposite. (which obviously doesn’t mean I’m right or even know because I honestly don’t. Just going by what I’ve read in the past) I’m not doubting you at all I just like knowledge. I’m open minded and like to learn. I researched years back when I was painting latex over oil and that’s just what I’ve always gone by. I didn’t use tsp but scuffed and painted. I kind of remember priming with oil based primer first but can’t remember for sure. We lived in that house for about 8 years and it was fine when we sold it but I scuffed and took the gloss off. I’m sure if primer was recommended I used it.
You can put oil on top of “Failed water based” for that is has to be very porous and oxidized. I did several like that in 2016 using Wood Defender Semi-transparent Cumberland Brown and they still look good today. I did tests to ensure it would work and a penetrating stain is not the same as oil based paint. Oil based paint does penetrate some but still sits mostly on top. Water based penetrates some too though. They both use a different means to adhere than penetrating stain does.
I just googled and there’s a lot of contradicting info out there both ways. Most seems to say latex over oil is fine if properly prepped. (as you stated) Some say you can do oil over latex and even more say you can’t unless you first prime with a sealer. Others say only on the interior as the exterior expand and contract at different rates causing the latex underneath to wrinkle and the oil based to come up. Some say that will happen regardless of interior or exterior.
Paints cure differently that stains. As a paint cures it contracts and that’s why the prep is so important. If the surface isn’t properly prepped the paint will literally pull itself off what ever it underneath it.
This again goes back to the penetrating oil verses paint, they just don’t work the same way. That said I did a fence in Sherwin Williams oil based Super Deck last year and it looked like crap. I ended up stripping the fence using DSR-50 (potassium hydroxide) from Power Wash.com and then repainting with Super Deck solid. I still wasn’t happy with it when I was finished but I drove by there a week later after everything settled in and it looked great. In fact the guy hired me to do the deck at his office for another 2k+
Now I’m even more confused. I wonder if there are so many varying opinions because different paint manufacturers have always recommended different ways depending on their ingredients? Maybe it also has to do with climate so different areas of the country have different opinions? I guess in the near future it won’t really matter since they will all be banned.
Now about concrete sealers. I know how to tell the difference between oil based and water based stain thanks to @MDA1775 How do you go about telling the difference between oil or water based concrete sealers?
In my limited experience with sealers are more of solvent verses water based issue. Both are carriers to get the sealer into the concrete. I’m having very good results with SEK Sure Bond Sealers
BTW, everything I have stated is as it relates to exterior wood applications not interior or exterior house painting.