Not to be the unhinged theorist in the Locked Tomb fandom but the Resurrection Beasts and Alecto have some peculiar themes that just tie too perfectly into radiation.
Like the blue light with Varun. Because if theres a real world example of a haunting blue light you never want to see in person ever, it's this:
Also, Nona does not want and probably can't really eat, which is both a running gag but also one of the first sympthoms after somebody gets radiation poisoning. And at the end of the book, her condition deteriorates.
And even from a narrative point of view: John Gaius used to be a scientist. He wanted to save everyone. He also kinda took the soul of the earth. He embodies powers that, if kept in check, can help many but they can also spell untold destruction. It just works. The resurrection beasts and their rampage basically being the equivalent of a melting reactor would mean it is still John's fault and it fucking is so I will just keep believing it.