Job titles vary wildly from company to company. There is absolutely no guarantee that a "junior" in one place is the same as a "junior" in another. Same thing goes for "senior", "staff", "lead", "1,2,3", "3,2,1", or even "VP" (a title which means virtually nothing in this era of fleeting technology start-ups)
If you're talking about certifications and degrees, those are relatively fixed credentials.
I have never heard of anyone getting an offer withdrawn because they failed to very exactly indicate the company-specific title on their resume. No one cares about the difference between a "Associate level 2" and a "Level 1 staff engineer".
On the other hand "junior" usually implies a vague sort of rank, it suggests more than just a meaningless level number. Some people really get hung up on silly inconsequential details, and as you can see, it can cost you the chance.
However, as you noticed, you got more response without the "junior" keyword-- so you might have lost a chance because of that too.