Excel document unlocks after being modified and saved

1. install Nuxeo 7.10 HF27
2. install Drive client 2.4.5 on Windows 10
3. create a user
4. synchronize the personal workspace
5. on client create a word document and close it
6. wait for synch with the server
7. open the word document
8. wait for lock notification and check the server for lock too
9. modify the document
10. save it but don't close it
11. wait for sync to finish
12. the document has been synchronized but remains locker (all ok)

Now do the same scenario with an excel document and observe there was no notification but the document has been unlocked.

The same can be observed when the computer is sleeping.