By splitting your Access database you separate the application into the front end and data into the back-end. This is a good practice for all software including Access applications. That’s why I recommend splitting the database. It’s not just for multi-user applications/databases. If you spilt the database, any web tables in that database will not be moved to the back end database and will not be reachable from the resulting front-end database.
Access database should never be opened by more than one user at same time. Access is supposed to be able to create a multi user database. The way is to split the database into app (front end) and data (backend). Each user will have a copy of the app (front end) that is not shared. The data (backend) is shared by having each user’s app (front end) link to the tables is the shared back end. Only the app is actually opened by access directly.