Yeah, you might not get the faster RAM running at full speed, and RAM above DDR4-3200 typically tends to be priced disproportionately high for very little performance gain.
Even if it's not priced significantly higher though, you should also pay attention to the RAM's timings, where lower numbers are better for performance, when taken in combination with the RAM's frequency. There's some 3600 RAM that's priced similar to 3200, but with a CAS latency of 19, compared to the 16 that is typical for 3200 memory. So the RAM might be clocked around 13% higher, but CAS latency is around 19% slower, which could actually result in it offering slightly less performance in some scenarios. To get DDR4-3600 with better timings than that, you need to pay significantly more than what most DDR4-3200 RAM costs. And unless you are doing certain memory-intensive tasks, that money would probably be better spent on other parts of your system that will have a greater effect on performance.