The instruction video you see, is a web page, not a native mobile page. The native mobile platform does have some restrictions, as it a new platform and there is a lot of new development is in progress. But in this case, it makes sense...
The reason you can not call a microflow, is that you microflow is executed on the server, and you mobile app should work offline too… though… since 8.8 you can call a nanoflow, check if you are ‘online’ and if you think it save you can call a microflow. Note that calling a microflow have some limitations too, see https://docs.mendix.com/releasenotes/studio-pro/8.8#new-features
Thank you Andries.