When creating a new Text Block, the dialog starts by requesting a Style. If you select one the following fields are set to match that Style except for the Font. To set that to the Style’s font you have to reopen the Style dropdown, go to the Style you just selected and click on the now visible right arrow to reveal a ‘Remove Overrides’ option.
This is convoluted and not intuitive. The whole point of a Style is to standardise annotation appearance. In a new Text Block the font should automatically follow the selected Style by default.