Some clever sleuth I follow may have a theory.
There was a tweeted press release in August 2022 from Scobie, saying he had sold the World English rights to his (as then) untitled book to Dey Street/Harper Collins UK&Commonwealth/Harper Collins US.
Publishers either buy World Rights or World English Rights. World rights means one publisher publishes all over the world and deals direct with local translations.
If the author sold only World English Rights to the above mentioned publisher, he held on to his foreign translation rights. He would be able to sell the foreign translation rights as separate transactions through his agent to local foreign language publishers. The foreign publishers would not have anything to do with the publisher with the World English rights - they would have their own individual deals through the author's agent.
So Harper Collins, the publisher of the English language version, would not have sent the manuscript to The Dutch publisher, Xander. OS's agent would have - sending whatever OS gave him to send as the final manuscript for translation. There's a possibility that the Dutch manuscript could have been different to the one sent to his English language publisher, because it was part of a completely separate transaction.
Scobie said in his interview on This Morning that his manuscript gets "licensed" to other publishers in foreign countries. That statement only makes sense if his agent is licensing the manuscript off one deal at a time to foreign language publishers. And that's where an old/different version of the manuscript potentially could have sneaked into the "pile" or file being licensed off.