How to reproduce:
1. Create a new project
2. Open the Profiler window (Window -> Analysis -> Profiler)
3. Change the Profiler Modules so that only the 'Memory' Module is displayed
4. Create a new Script in the Project window
5. Switch to 'Detailed' information type in the Profiler instead of 'Simple'
6. Right-click on the newly created Script and select 'Reimport'
7. Start recording with the Profiler
8. Stop Recording
9. In the Profiler window press 'Take Sample Editor'
10. Expand 'Scene Memory' -> 'MonoBehaviour'
11. Make note of the count for MonoBehaviour
12. Repeat Steps 6 to 12 again
13. Notice the count increases with each import

Expected results: "MonoBehaviour" count stays the same with each import
Actual results: "MonoBehvaiour" count grows by 1-3 with each import

Reproducible with: 2019.3.0b10, 2019.4.19f1, 2020.2.3f1, 2021.1.0b5, 2021.2.0a3
Not reproducible with: 2018.4.31f1
Could not test with: 2019.1.0a1, 2019.3.0b9 (No option to "Take Sample Editor")

Note: MonoBehaviour count in the Profiler goes back to normal if you reimport while recording