It doesn't matter if the decoder had been fitted by the customer. The loco was sent back fully fitted with decoder and speaker and I for one would expect it to come back fitted if it was mine.
I used to work in model railway trade/retail and the branch I worked in, I did all the loco service work on my own if the loco was out of warranty or just come in for a service, If they where under manufacture warranty then those went to the company involved for sorting. Not once did a loco get sent back to the customer with things missing or not fitted back inside.
EM2 aint a small cube speaker. What every Hattons do now, It's still poor service regardless of what you think.