I may be reading too much into that, but my interpretation of “seamless” is that Z-Wave/Zigbee devices will be moved over to Edge and the fingerprinting process will map them to an “appropriate driver”. My own experience with legacy z-wave devices tells me that it’s possible to move from a DTH to Edge without exclude/include, though at the moment it requires exploiting a loophole. Admittedly, it’s speculation until a ST staffer maps out the customer transition and firmly says “You will not need to exclude/include your z-wave/zigbee devices as part of the transition”, but the alternative - that they’re expecting all of their customers to think “seamless” means hauling their hub up a ladder to exclude/include their devices - is ridiculous.
Let’s not conflate “custom DTHs” with “devices using custom DTHs”. You’re correct that ST is not converting custom DTHs by rewriting community members’ Groovy code in Lua. However, I would again argue that “seamless” will not mean deleting/re-adding a device. I’d also argue that ST isn’t going to keep the Groovy cloud going just because someone is still using a custom DTH. So “custom DTHs” will not be rewritten, but “devices using custom DTHs” will be mapped to an Edge driver.
Also, please don’t take one sentence out of context to play gotcha. The post you decided to quote was in response to the specific question “what do i do with this code?”. The code in question was a snip of the fingerprints for two specific Somfy zigbee devices in a stock ST driver. I stand by that sentence in its context, as I fully expect those devices to be automatically transitioned to that particular Edge driver at some point in the future.