Connect excel to ms-access front end database
I would connect directly to the Access database back-end part. Why involve the front-end?

...As I understand splitting access prevents from data corruption in shared database (when users open same file). ...

This is not quite correct. Splitting an Access database ...


  ...Splitting a shared database can help improve its performance and reduce the chance of database file corruption.


Source: Split an Access database (Microsoft Office Website)

...If I use a SQL command within excel and send it directly to the back-end, then I am using excel as the front-end (and that clears the issue, am I right?)

Same as above. You are minimizing the risk when splitting an Access database into a front-end (form, queries, etc.) and back-end (data), but you are not eliminating the risk of data corruption. 

Consider using a database system like Microsoft SQL Server, Oracle RDBMS, PostgreSQL or MySQL to further reduce the risks of data corruption.