It's doubtless unproductive and wearisome to remove seeds from each seeded grape before placing each into a blender. But if I don't remove seeds, can the seeds:
mangle or mar the blender blades?
chip or shatter the blender's container/jar?
In short, no. You could blend pencils and pens with most modern blenders and there's no damage to the blender. Fruit seeds won't be a consideration except in use of the blended fruit. You might need to strain the output to remove bits of hull.
The ‘real’ solution is seedless grapes.
Blending seeded grapes in itself isn’t any issue for the blender, it simply won’t care at all… however if you blend too long you will break through the seeds’ outer jelly layer & start to grate the seeds themselves, which will make the resulting purée bitter.