2% Digital Tax Charged on 'Free' Shipping Promo – Anyone Else Noticing This?

Has anyone else noticed that Amazon is applying a 2% digital tax on shipping fees, even when the customer qualifies for free shipping through a promo?

I found this in my transaction reports where the customer met the spending threshold for free shipping. Amazon charges the shipping fee to the customer, but then refunds it, so the customer doesn't pay for shipping, and we, as sellers, aren’t impacted directly.

However, Amazon is still applying the 2% digital tax on the initial shipping fee (in this example - £2.07 excl. VAT), even though it gets refunded. For larger shipping fees, often £4.99, this results in an extra £0.08 digital tax per order. Shouldn’t the digital tax on shipping be refunded too, if the shipping itself is refunded? Or am I missing something here?