Apex class behavior with Null instance of Sobject

Apex_Sobject_member_to_null.cls

/*
 	MyController cnt = new MyController();
	cnt.tst.Name = 'test';
	cnt.tst = null;
	system.debug('Test outside: '+(cnt.tst.Name == null));	//Test outside: true
	system.debug('Test outside: '+(cnt.tst == null));	//Test outside: true
	system.debug('Test outside: '+json.serializepretty(cnt.tst)); //Test outside: null
	cnt.myMethod(); //Throws null pointer exceptions
 */
public class MyController {
    public Account tst{get;set;}
    public MyController(){
        this.tst = [Select Id, Name From Account limit 1];
    }
    
    public void myMethod(){
        system.debug('Test inside: '+(tst.Name == null)); //Throws null pointer exceptions
        system.debug('Test inside: '+(tst == null));
        system.debug('Test inside: '+json.serializepretty(tst));
    }
}

If the Sobject member is nullified, outside the class the member still is accessible (even if null) while inside an instance method the same system.debug('Test inside: '+(tst.Name == null)); throws an exception

Some ref: http://salesforce.stackexchange.com/questions/135750/strange-behavior-with-null-sobject-in-apex-class but this does not explain why the member method fails

Yes, I noticed this behavior when writing Apex in the past, the way you can make this more controller is by using 'this' keyword., So in your myMethod() if you change to below, it should give you the same results as Execute Anonymous. SObjects have a behavior of throwing NPE if they are not initialized.

system.debug('Test inside: '+(this.tst.Name == null)); //Throws null pointer exceptions system.debug('Test inside: '+(this.tst == null)); system.debug('Test inside: '+json.serializepretty(this.tst));

@logontokartik in this context this.tst and tst refers to the same inner member, there are no other "tst" variables, how did you explain this regarding the Apex engine?