Reproduction Steps:
1. Open project
2. Build to iOS
3. Open Xcode 8+
4. Set GPU Frame Capture to Metal
5. Build app
6. Attach Debugger
7. Capture GPU Frame
8. Look at Standard "Current ms"
9. Resume app
10. Disable particles - UI button "Turn off"
11. Capture GPU Frame
12. Compare Standard "Current ms" with the last one
13. Notice that value increased when particles were disabled

Expected behaviour: When particles are off Opaque geometry are drawn at the same amount of time or even faster.
Actual results: On some devices drawing time increases when particles are disabled.

Reproduced on versions: Unity 5.3.7p2, 5.4.3p3, 5.5.0p1, 5.6.0a6
Reproduced on devices: iPad Air iOS 8.1.1, iPad Air iOS 9.1, iPad Mini 2 iOS 10.1.1
Did not reproduce on devices: iPad Mini iOS 9.3.5, iPhone 6+ iOS 10.0, iPod 6G iOS 9.3, iPad Mini 3 iOS 9.3.2
Reproduced on Xcode 8.1 beta 1