Part I agree and part I don't.
chat with someone is never the same as sitting face-to-face.
When you talk with 3 or 4 people, chatting simply lose something on the way.
It start from simple response time that are much larger in chat and go into much more.
Measure hours as sign of productivity is never good, but ignoring hours is bad as well.
Estimate how long it will take you to accomplish something is the hardest and very important quality of everyone including developers