It’s not meant to be a single digit multiple of the UK tax, I don’t know where you’re getting that from. The things which the article mentions as being single digit multiples are:

In 13 countries, acquisition taxes for such an SUV are more than three times higher than the UK’s

£3,200 in the UK, but the sale would incur taxes of £66,600 in France – driving UK SUV sales to four times the level in France.

And the headline figure is “up to 20 times”, which roughly matches the £66k.