Garbage collection unexpected results

During some testing using the emulator and pushing the code to RAM I found the following oddity while logging the output from process.memory(), the same occurs if I run on the watch via RAM. If I push the code to a storage file and its run from there it works more as I would expect.

I have a test method inside an instance of an App class which runs for the duration of the program as follows:

setup = () => {
        this.route = RouteHelper.loadRoute('feature_test');
        this.nav.setRoute(this.route);

        this.nav.setZoomLevel(5);
        this.nav.startRoute();
        
        //print mem here
        
        // BangleMock.start();
        
    };

printing out the memory at the comment part of the above script gives around 2000 free. Its the same if I do this outside the method after the block has finished.

If I add a timeout to print the memory usage after a few seconds:

setup = () => {
        ...
        setTimeout(this.printMem, 3000);
    };

Free memory jumps to around 9000.

That code block doesn't contain any async functions. Does anyone have some insight into why a big chunk of memory is being freed a few seconds after execution, rather than at the end of each block scope.