As a heraldic image, the VM eagle (if it is an eagle) would have its wings "splayed", like Sigismund's, so that is something they have in common. However, the division of the VM's feathers is decidedly un-heraldic. In heraldry, the large feathers are in the mid section (blue), hanging under the wings. The feathers in the red section are either absent or small. In the VM though, the top feathers are larger than the ones in the mid section, and they extend well above where the creature's head would be.
In heraldry, the tail generally goes down first, and then outward. For example, in the case of Sigismund's seal, you can see that there is first a vertical column, and then almost horizontal feathers. In the VM, we see something completely different, and you will be hard-pressed to find a heraldic eagle that looks like this.
I'm not saying that these differences must be explained, maybe this is just the best way to draw a heraldic eagle in a root. But I don't find the resemblance as straightforward as some people claim.