Not so. Items should be marked microwave safe. I have had sales people tell me up front that an item was not safe for the MW. Although I have ignored them at times and items are fine. This hasn't been with a Miele speed oven. What do your docs say? Or perhaps contact Miele. Others will chime in with better info than me.

there can be bubbles in glass and that can cause shattering in mw.

Glass suitable for ovens needs to be tempered glass (Pyrex, Duralex, etc.)

Speed ovens work differently than microwaves, with heat that can undo most non-tempered glass. There's a bigger range of tolerance with microwaves, especially if the microwave is an older, low-powered type, but even then you're best advised to stick to items known to be oven or microwave safe (high-fired porcelain, tempered glass). Non-tempered glass (especially colored glass such as Depression glass) often contain metals that don't react well in the microwave.

Speed ovens heat from the bottom in addition to the MW feature, so you need more "oven proof" items - I have been using Corning so far as I am chicken to try my fancier stoneware dishes - even though they should be fine.

The breakage we had was when we were using the microwave solo function. I never had a problem with the Sophie Conran bowls before but maybe I just got lucky for a long time. I am not sure they are microwave safe. I have been using my Thomas for Ronsethal Loft porcelain in the speed oven and haven't had any issues, so far at least. They are supposed to be microwave-safe.

Interesting.
Maybe they just hit end of life or had micro cracks that moisture invaded

It's also possible that the microwave function on your new speed oven is much more powerful than your old standalone microwave.

A microwave by itself isn't going to damage any glass container. Glass containers will fail when there is a big temperature gradient, like the bowl is very hot and you put it on a cold surface, or vice versa, or something in the bowl gets very hot in a very small focal point while everything else around it is cool. Perhaps that is what is happening in your new speed oven.

The other issue with glass cookware is how you clean it. Never use an abrasive cleaner of any kind on glass cookware unless it is specifically labeled as ok to use on glass.

I just remember seeing a special on Pyrex and the new Pyrex was shattering -(and I assume the other brands had the same problem) - They switched how it was made and showed pictures of the shattering pyrex..