Thank you very much, I think I understand what is the problem now. The field there is not actually a single text field, as it consists for a checkbox + input, and I think ACF stores them as a serialized object, so it contains additional string information.
Would it be an okay solution for you to use the additional seach tags field?
I have enabled that meta box for the products editor screen, and added the G1320 keyword to this product on the editor: https://i.imgur.com/1Fs6qFk.png
That field is designed specifically for these search tags. I have tested on the search instance to search for ‘G1320’ and it returns the correct product now, only on full exact match on that field. Please let me know if this is acceptable solution for you.
If yes, then all you need to do is just add the keywords you need into that field.