It seems to be if nothing is selected (the value is null) it will have a spot to allow you to keep the null value.
Once you select a value, then it will only allow you to select from valid choices. Please see the link for the column setup screen and editform screen shots.
I was testing on a document library, where it worked as expected.
I tried it on a normal list and I am seeing what you are seeing.
All Asynchronous events end with ‘ed’ letters like Site Deleted, Field Added, Item Added etc.
Now, let’s talk on the subject of Synchronous events, all Synchronous events occur before the event, which stop the code to execute.
To configure the Data Source control to handle insert, update and delete click “Advanced...” button. Click “Configure List View...” option as seen in the above figure to choose the display Layout for the List View.
Thus, we have learnt how to provide edit/update/delete and insert feature for List View Control.
You can work on items and mess with them, then when they are ready, you send them to the records center for read-only archival.
Any other solution you come up with will allow an administrator to modify the existing documents / list items.
These fresh events are intended to meet up the requirements and for better elasticity.
SPWeb Event Receiver Web Adding: event arises prior to a fresh web site is created, we can control the website to create or not to create by Web Adding event, then no Share Point site is created and the provisioning process is not started.
In Grid View, the Edit/Update/Delete feature is an inbuilt one and can be achieved without writing a line of code with the help of Data Source controls.