It is now a preference.
The default preference is to not change any button text layers when linking, but to change the button name in the Layers panel to the name of the linked object.
However, you can set the preference to sync at all, or one of several of syncing behaviors when linking buttons:
Do not sync anything when linking (pre-Encore 2.0 behavior)
– or –
Sync
1. Button name to linked object name (this is considered handy to instantly see which button is linked to which object just by looking at the Layers panel)
2. Button text layer to linked object name
3. Button name and text layer to linked object name (Encore 2.0 default behavior)