I'm afraid antiviruses spy on you, especially free ones.
Windows spies on you more than any antivirus software. Windows is a privacy nightmare. Check out the links I shared in
this post. Even if you try to sanitize Windows, turn off all the extra features, block or disable as much of the privacy invasion as you can, it still transmits data back to Microsoft and a variety of third parties about your device and what you are doing on it hundreds or even thousands of times an hour.
If you are using Windows, then whether your antivirus is spying on you is the least of your concerns.
Actually, you are 100% right but if you are using Windows, why should you double the number of spies? It will also slow-down your computer too. If I had to use Windows and Electrum, I simply would not visit malicious websites, unknown URLs, wouldn't open unknown emails or would use only separate email.
I really don't think one needs to use Antivirus if the person only visits certain reputable websites from specific device.
Btw in ideal case, one should dedicate one pc/laptop to privacy and another one for public activities, gaming and everyday life.