The echo knight feature Manifest Echo says (emphasis mine):
At 3rd level, you can use a bonus action to magically manifest an echo of yourself in an unoccupied space you can see within 15 feet of you. This echo is a magical, translucent, gray image of you that lasts until it is destroyed, until you dismiss it as a bonus action, until you manifest another echo, or until you’re incapacitated.
Your echo has AC 14 + your proficiency bonus, 1 hit point, and immunity to all conditions. If it has to make a saving throw, it uses your saving throw bonus for the roll. It is the same size as you, and it occupies its space. On your turn, you can mentally command the echo to move up to 30 feet in any direction (no action required). If your echo is ever more than 30 feet from you at the end of your turn, it is destroyed.
Attack of Opportunity mentions (emphasis mine):
You can make an opportunity attack when a hostile creature that you can see moves out of your reach. To make the opportunity attack, you use your reaction to make one melee attack against the provoking creature. The attack occurs right before the creature leaves your reach.
The description does not state that the echo is a creature, so am I correct to conclude that the echo wouldn’t trigger an attack of opportunity?