Is bitaddress or warpwallet generator considered a dapp? They aren't tied to centralized server when you use the application to generate your own addresses and it can run by itself.
I think this comes down more to semantics than anything else (and thus might make the question off-topic as opinion based), but I'll give it a shot.
I would classify BitAddress or WarpWallet as standalone programs (or even scripts, although I would lean towards program since they are interactive), much in the same class as a calculator app. Yes, they don't rely on a centralized server (barring distribution, which could also be done over torrents or something). They don't work in the same way as you would expect a dApp to. There is no data replication/distribution to peers. There is no interaction with a larger network at play here. They work fine in isolation and have no need to access any external resources.