If you look in your itemized order history for a given item, the first link in the row is to your actual order. On your actual order page, there is a list of installer information underneath it. That installer information appears to be live data. That is to say, it’s pulled from the item information when the page is shown to you. If this is true, that means that it’s usable as a source of ‘what has updated’, because the indicated installer information will have a newer version number than when you bought it.
If that’s true, and it remains so, it might be possible to write a tool that downloads all that information occasionally and lets you know when stuff has changed.
There’s a lot of ‘if’s in there, admittedly, but any chance of being able to work around DAZ’s timeframe and develop a tool that does stuff that they don’t have the time to take on yet is an interesting chance.
e.g. This block in your order details: