Hi Galén,
Thank you for posting your concern.
You may use KeywordMatchType field as it returns the match type for the Keyword (such as EXACT, PHRASE and BROAD) so that you can identify the match type of keywords without the special symbols. However, the said field returns a value Broad for both Broad match and Broad match modifier. With this, you would need to identify by checking if the Criteria field includes + in the returned value.
Please let me know if you have further clarifications.
Regards,
Hiroyuki
Google Ads API Team