Does anyone know if Rick signed less Heroes of Olympus copies compared to the rest of the series?[all]

Im trying to collect all of them signed.I have completed the Trials of Apollo with extra copies,they all seem to have their designated signed page and will even say signed copy at the back by the bar code.Senior Adventures and the Nico Spinoff have the same tell,I suspect because of the popularity now he sings more books in bulk that get sent out to stores.

The original series Im one away from also completing it and those have none of the special designated signature page.But I have seen a few floating around with the old barnes and noble autographed sticker.Own multiple signed copies,specially Sea Of Monsters.

As for Heroes of Olympus I only own Blood of Olympus and any signed copy I see sold online seems to be mostly uk copies.Did Rick not sign many copies during those years if anyone knows the lore or Im i just having bad luck finding these four for cheap ?