shortcode_atts_{$shortcode} filter not being applied

I've been trying to use a shortcode_atts_mb_frontend_form filter to set/override some default shortcode attributes. Specifically I want to force a ReCaptcha check on a certain FE form without relying on an editor to use the correct ReCaptcha keys in the shortcode.

However, it seems that the Shotcode::shortcode function of MB Frontend Form does not use shortcode_atts before it renders the shortcode.

A simple call to shortcode_attrs() with no defaults would allow me to override the shortcode attributes that editor uses (or doesn't).

Am I able to achieve what I need another way, or do I need to request this as a new feature/bugfix?

thanks

Saul