It’s unfair to call it insecure because you don’t know that. Your file was insecure as a result of your bad choices in how the cryptography is used by the software. I’m not blaming you for those bad choices because you don’t understand how each algorithm interacts with the different configurations. You probably thought you were making a good choice by choosing AES. Normally this would be an fabulous choice.
I’ve not read the whole topic but Brian seems to have briefly discussed the fact that BCArchive is intended for experts and I agree with him on that. If used by an expert it should be fine but in the hands of a normal user it’s dangerous because it doesn’t stop you making stupid encryption choices.