You're right, but there are a few subtle differences here and there that often make Windows Forms recognizable.

The best example I got off the top of my head is KeePass v1 [0] and KeePass v2 [1]. v1 is written in C++ with native controls, and v2 uses Windows Forms.

If you look at the menu bar and the toolbar, you'll see a difference. Most notably the drag handle on the left, and the search box on the right, in v2. The difference is often a bit easier to spot on Windows 7.

[0]: https://keepass.info/screenshots/main_big.png [1]: https://keepass.info/screenshots/keepass_2x/main_big.png