To be more precise their claim is that birds evolved from non-maniraptoran coelurosaurs.
And yet when they compare a "dinosaur" to a bird, they do not take a drawing of a non-maniraptor coelurosaurian, (eg. tyrannosaur) but they take a drawing of a non-neornithine Aves (eg. Ichthyornithes) creature and compare it with a modern bird.
This of course is irrelevant.
The issue is NOT WITHIN AVES but between non-maniraptor coelurosaurs and maniraptors.
Here are some non-maniraptor coelurosaurs.
Tyrannosaur:
Compsognathid:
These are believed to be sister taxa to the non-maniraptor coelurosaur ancestor of birds. But as we all know, the dino to bird theory enthusiasts never present any pictorial representation of any purported non-maniraptor coelurosaur, bird ancestor.
So who knows what it looks like.
But certainly if we want to understand what the dino to bird theory is actually claiming, we need to compare the non-maniraptor coelurosaurs to modern birds and not non-neornithine Aves creatures to modern birds.