First of all, remember that a keyword is a word or a set of words that you create to target a certain ad.
Search results on broad match keywords work like this: Your ad might show up when a user’s search term includes relevant variations of your keyword. For example, their search term might include one OR more of the words in your keyword, in any order, or it might be a synonym or a variant of your keyword.
When you include the broad match modifier, you make the broad keyword matches more specific. By adding a plus sign (+) to the front of a word (within your keyword), that word must match exactly in the search. The other words (that are a part of that same keyword) with no plus sign (+) can still match a variant of that word.
When Finch optimizes your campaigns and you are using keywords with broad match modifiers, we preserve them. We launch the keyword the same way as a broad match modified keyword. We go further and create additional keywords from that broad match keyword. We remove the plus sign (+) and we do a broad match, a phrase match, and an exact match. In other words, we create additional match types even if you were not previously using them thus enhancing your campaigns.
Read about keyword matching options on Google AdWords.