Excel won`t send UNLOCK to WebDav when exiting Excel

Question

Hey there,

we implemented our own WebDav Server in an ASP .NET Core Application to provide files from our own Repository. As far as we investigated we followed all standard protocols and responses provided by the documentation.
All editing and lock/unlock functions are working propertly in Word and PowerPoint.

In Excel we have an issue where the file won`t get unlocked when Excel is closed, as say by just closing it by the X Button. The user gets asked if to save the file.

After the file is saved properly through the WevDav Server no UNLOCK request is made from Excel.

In Word and PowerPoint the UNLOCK requests are made when closing via the X Button.

When the user closes the file explicitly under File -> Close, the UNLOCK request will be send and then gets unlocked.

As for my question, is that intentional? When closing excel the file clearly also will be closed or not? Why does that work in Word and PowerPoint?

We're using Microsoft Office Pro Plus 2019

Best Regards

Michael Trinkies