List Page forms doesnt allow to override methods in AX 2012

it is the Standard AX 2012 behaviour of the List Page forms it doesnt the override methods in the form.

Here is the example - created the Form of ListPage, it doesnt allow to override the form methods.

 

In the case of the normal forms - it allow to override the forms methods

So try by creating the form by having the formtempate - property as None(i.e. normal form)  and try to override the form methods and then change theform property FormTemplate to ListPage - to show a message the override methods will be deleted as shown in the below screen

 It is the standard behaviour of AX 2012.

Source - http://dynamicsuser.net/forums