Windows Phone app update weirdness

I have a SIM-less HTC Surround that is used to try out Windows Phone apps. It works like you would expect for a WiFi-only device for the most part. The one exception is that the Windows Market app does not update software for it as expected. In fact, until last week, no app had been updated in a couple of months. Even going to the product page in the Market app does not force updates to appear. So, imagine my surprise when I saw not just one but 23 apps ready for update recently. I haven’t seen any other updates since then even though several apps for my HD7 (which has a SIM) have been updated in the past few days. Even the HD7 does not get updates when expected, however. It sometimes gets updates a week or more after an app was reported as updated by others.