Hi Abraham,
According to sap.m.Input code, I guess the default filter is set to 'StartsWith' filter operator.
I didn't find a way to change it, as you already mentioned if we go through explored sample even that way it is not working. However you can raise this as an issue and check with UI5 team? Issues · SAP/openui5 · GitHub
Regards,
Sai Vellanki.