The longer Blaze holds the shield the heavier it will get--until it's something comfortable for her to use. The shield's heft seems to fluctuate to meet the user's needs. In all likelihood she's feeling it's true weight.

And she and Ghost will be forgiven for laughing when Steve drops to the ground when Blaze offers it back to him. He's shocked by the change in weight though it is a fleeting thing.

"Just...just me." Steve admits when he can stand up again with it. "I've been practicing but well..." He shrugs. "I don't really know what I'm doing. I've been trying to learn how to throw it."