Hypothesis 1: The spider knows the bee is laying eggs and can possibly make a meal of the babies and the bee either thinks this is worth the risk, or started the nest before realizing the spider was there and doesn't have time to find another.
> “Judging by the size of that spider it would be quite a task for it to grab that bee and it would get stung,” he said.
Hypothesis 2: The bee and the spider are in some kind of behavioral stalemate, they both know that the risk of a bee sting is greater than the potential of a bee meal, so they tolerate each other.
I would still wonder whether the bee can recognize that the hole was a spider burrow if the spider isn't present. If the bee can't, then I would wonder what the situation would be for each of them when a spider was out hunting and came back to find a bee already building a nest.
In any case, it looks like there is some good science that needs doing, very cool.
Another recent discovery was the amazing Peacock Spider... https://en.wikipedia.org/wiki/Maratus_volans.
There are tons of tricks like this that the average Australian kid (used to?) learn .. another great trick is to take a gold coin with you while snorkelling, and use it to lure octopus out of their lairs .. they find it irresistible. I've had hours of fun with that trick.
> “I jumped back because I am shit-scared of spiders; I thought it was a bloody spider.”
And possibly has some time on his hands being a railway employee in the bush :-)