This is normal behavior for the ProxySG.
These values also include bandwidth used by normal GIMS (Get-If-Modified-Since) requests. It's not specific to "adaptive refresh"ing of objects.
Because the ProxySG is a caching device, it keeps track of objects and their expiration dates. When an object expires, the ProxySG would normally automatically retrieve the object. With adaptive refresh disabled, the object sits until it's requested by a client, at which time it would be retrieved. Since the ProxySG is not performing adaptive (or automatic) refreshing of cached objects until a client specifically asks for that object, expired objects must be retrieved immediately when clients make requests, rather than gradually over time in the background.
Please note that if there are a lot of objects that need to be refreshed all at once during a period of higher load/utilization, the ProxySG will need to work harder than if those objects were refreshed evenly over time.