Am I right that "MyModel>title" is just temporary at this moment (during loop)?
I'm not sure what you mean by temporary. When the aggregation binding happens, the binding path of the buttons will be resolved to,
1st btn - MyModel>/subData/0/title
2nd btn- MyModel>/subData/1/title
You can make use of the UI5 diagnostics tools (ctlr + Alt+ Shift + s) to view the controls binding paths info during the runtime.