Here's the thing. You said "dinosaurs are reptiles."

Are they in the same class? Yes. No one's arguing that.

As someone who is a scientist who studies dinosaurs, I am telling you, specifically, in science, no one calls dinosaurs reptiles. If you want to be "specific" like you said, then you shouldn't either. They're not the same thing.

If you're saying "reptile class" you're referring to the taxonomic grouping of Reptilia, which includes things from snakes to turtles to lizards.

So your reasoning for calling a dinosaur a reptile is because random people "call the scaly ones reptiles?" Let's get fish and pangolins in there, then, too.

Also, calling someone a human or an ape? It's not one or the other, that's not how taxonomy works. They're both. A dinosaur is a dinosaur and a member of the reptilia class. But that's not what you said. You said a dinosaur is a reptile, which is not true unless you're okay with calling all members of the reptilia class reptiles, which means you'd call microraptors, jackdaws, and other birds reptiles, too. Which you said you don't.

It's okay to just admit you're wrong, you know?

What I also find interesting is that the nearest extant animals to birds are crocodilians. Both belong to the archosaur clade, even if there's around a 240 million years gap between them.

As you say, birds can be classified as belonging to reptiles under the cladistic route, but they're quite radically different to the reptiles that live today, so are seen as not really reptilian. It's not surprising, seeing that the link between crocodiles, true reptiles in all senses, and birds were the dinosaurs, who disappeared 65 million years ago. A whole lot of evolutionary change in that time.