The problem is that in order to be certified as a controller, as SmartThings is, all it has to do is to be able to establish the network and then send “basic” commands, and basic has a very specific meaning in the Z wave context.
Basic here means essentially on/off/dim.
Smartthings can do that.
The problem with the fIbaro 01 sensor is that it is using some advanced features, in particular multiple end points. Smartthings doesn’t handle multiple end point Devices very well in the official features. And didn’t handle them at all when it first launched.
For example, if you add the enerwave SC7 seven button light switch to SmartThings, it will only see the first button.
In that case, community developers have been able to create code which works OK.
Another example is the Aeon power strip, which has six outlets. Again, if you just add it to SmartThings, you only see a single on/off option. Community developers have created device type handlers which assign a virtual switch to each of the six outlets so you can control them independently.
There are other examples as well. I haven’t looked At any of the details for the two smoke sensors, but my understanding from glancing over the staff responses is that the device will require some code for multiple endpoints.
Speaking just for myself, that’s something I might do for a light switch, but I would never do it for a smoke sensor. Which might be where a Fibaro response came from.
Why? Because once you go to custom code, that device cannot run locally at the present time. That means if the Internet goes down, that device won’t work as expected in terms of communicating with SmartThings. Your Smartthings hub will no longer be able to understand its messages. And of course a fire is exactly the kind of a situation when you might start losing Internet or mains power.
Most customers who buy SmartThings products have no idea that this forum exists, and no awareness of the issues with local versus cloud-based processing. Imagine if they successfully set up a simple siren and lights alert notification when the smoke sensor detected something with no awareness that the smoke sensor alert would never be received by the local SmartThings hub if the Internet was off. 
SmartThings has disclaimers that it should never be used for emergency situations, but again, but most people never see those.
I don’t know for sure that Fibaro said “If you can’t support it locally, don’t support it officially” but I think it would be a reasonable position for the manufacturer of a smoke sensor to take.
Again, all of this (except for the challenges involved with multi endpoint devices in a SmartThings platform) is speculation on my part.
. I guess I could use a 002 and hard wire the battery terminals from my alarm as the 002 uses the same 12V batteries as the 001. But I couldn’t have a wired connection straight back to my alarm - it would need to be via a relay triggered by the ST hub - which I think is less robust than directly hard wired to my house alarm.