Yes, I also can confirm a this behavior.
Steps to reproduce:
- In Search Engines switch to Google search as default. Start page search bar is off.
- You just need to wait 2-3 days.
- 100% switch to Yandex-junk.
In Extensions I have UBOL (only) from Google store.
I don't have a partner applications or other unwanted bloatware. And yes, my PC already have installed antivirus engine (Kaspersky).
P.S. With a clear profile and without sync this behavior I can also confirm.