We appreciate and understand that you want to protect the users and you’re careful about security. In our case, there are a couple of things in various domains that make the classic mode required and why we are requested this.
Guardata users can have multiple mount points (many workspaces, plus time machine mounting), and select which ones are mounted, mount/unmount with a single click on a slider from the GUI. This uses extensively fusermount and unmount. This is not supported by fuse-support. At this point, after reviewing the fuse-support module, we expect guardata can’t run with this snap interface because of this.
Adapt to use the strict mode, would require some changes in the existing app, detecting that the app is used in snap, for example mount in the SNAP_USER_DATA directory. Our app can run on multiple platforms (Windows, MacOSX, Linux), and this is like Snap will be one more OS. It would require engineering time. Adaptation is even pointless as, explained in the previous paragraph, we think it is not even possible to run in strict mode.
Our app already benefits of great care to work reliably across many distributions (Python 3.6-3.8, Ubuntu 16 18 20). Also it is fully in Python so the portability issue is eased by Python. We already continuously test and make available the app (as Python wheel pip) on various Linux platforms. The snap store app is a way to make it an easy way for Ubuntu users to install the app.
Guardata is a fork from the Parsec system (in which we are also an official contributor through an signed mutual agreement), which is available on the snap store as a classic mode app.
We are a security company, and we are committed to provide the most secure experience for our customers, protecting their data and not to harm their machine. We have Apple developer ID certificates for Mac ans iOS for years, and an EV code certificate on Windows. We would bring the same level of quality to the snap store.