For far too many years, I was pedaling like you. I went to Power Grips and since I had always pedaled that way, I adjusted the straps so my foot would be in that same position. Wasn't til I did a fitting with a new bike that I was told my foot was in the wrong position, I needed to adjust the straps to get my foot in the proper position. Was puzzled as to why I had my foot in the wrong place for decades of riding. With Power Grips holding my foot in the right place, I found it a pretty natural, good feeling adjustment. Then I was on vacation in the hotel fitness room, and rode an excercise bike with no straps. Realized that with my foot in the proper position, I couldn't really keep my foot on the pedal as I spun around. Needed to pedal more with the toes to keep the foot on.

I think your position feels more natural when you don't have something that keeps your foot to the pedal, whether clipless pedals or clips or straps or some combination of shoes and pedals that is sticky enough. Otherwise, if your foot is more level, it is hard to keep the foot on the pedal, it is hard to pedal in a circle.

If you are riding clipless or with clips or straps, the answer should be easy, your foot should be clipped or strapped into the right position, and it will feel natural soon enough. If you are just riding flats with no clips or straps, then find some sticky pedals to help keep the foot on in that position (unless you can get a shoe that will stick enough with pedals that aren't so sticky). If that won't work well enough for you, it may be time to go clipless, or at least to clips or straps of some kind.

I would think that if the seat is too high, then you wouldn't be raising that issue, because you wouldn't really feel you can get more power with a flat foot, but maybe I'm wrong about that, it is at least worth checking on the seat height.