I think you hit the nail on the head right here. For the average person, quality of work suffers tremendously when it's done from a location where there's less physical monitoring than in a workplace locati0n. I've experienced this with customer service representatives... and you can tell very rapidly when one is working from home. Delays, poor sound quality, background noise. It takes twice as long to get the same outcome as you would get if they were in a workplace location.
Another concern is the retention of customer data on employees' personal devices. As someone who understand the importance of privacy, I don't want my data to be stored on some stranger's personal device! I never gave that type of permission to the company, yet with the rapid WFH changes that took place, we didn't even have the opportunity, as customers, to opt in or opt out of this.
While the superficial benefits of WFH are clear, the underlying downsides just carry on revealing themselves over time.
The privacy is an interesting thing in regards to this and there is very little oversight in most companies in how to deal with it. The company I ,work for doesn't have this issue, but there are still some issues.