c.Callback = @(s,e) getrsf_Callback(s, e, guidata(s))
That is to say, the String property of a uicontrol has no effect on callbacks: it is what the uicontrol displays.
When you create a gui using Guide then one of the things it does for you is to link in callbacks on your behalf. It does that by setting the Callback (or appropriate) property of the graphics objects saved in the fig file.
It also links the graphic object into handles on your behalf. It does that at the time it loads the gui by looking for Tag properties of graphic objects and creating fields in the handles structure for each valid Tag.
Note that these are two separate processes: callbacks saved as part of the object properties, and glue logic when the gui initializes that creates handles according to Tag.
When you create a graphics object yourself you need to set the callback property yourself. If you want you can also add the item into the handles structure.
