That is because those references would be ambiguous if you didn’t include the second author to distinguish them from one another. If you want a different way to distinguish them, you will need to select it in the output styles citation template section’s “ambiguous citations” - delete the check in front of “add authors”. That is - if you prefer year letter format to distinguish them.
And perhaps even removed the “add initials”, although APA does want you to distinguish different authors with the same surname, this often is incorrectly applied if an author’s name isn’t entered consistently and the best way to fix it, is to copy the author name so it is the same in all records.
