I've seen this happening with my RTX 2070 Super. In Final Fantasy XIV, if I let the card go full ham, it'll happily go up to around 220W. But if I power limit it to about 80%, I get zero performance drops.
So I took this further and undervolted my card. At what I have set currently, it's limited to about 1935MHz but sits at 0.950V and consumes about 75%-80% as much power. And I added another profile on MSI Afterburner to see how low I can get it to still run the stock boost speed of 1800MHz. It goes down as much as 65%. Normally if I let the card do its thing, it can get up to about 2050MHz. So I could get a theoretical performance gain of ~14%, but I'd have to consume at least 70 more watts getting there.
Similarly I noticed when I was doing Handbrake runs, I left my CPU's turbo disabled on accident. However, I found that I only lost about 15% performance, but the CPU was also consuming 60% of the power.
I'm starting to not see the point of full on turbo boosting unless I need to polish my e-peen.