This is a limitation of the real time engines. The real part has one sticker but because it is transparent, you can see it on the other side in real life.
In 3D, you can define if the back side of a face is visible or not. So from here you would think that I just have to turn this feature on. However, rendering transparent elements in real time has a high calculation cost and tricks are used to go faster. To summarise, seeing the sticker through the back face would be possible but it also means lots of ugly artifacts. The decision has been made to turn off this feature.

A trick that has been used in the past was to mirror the sticker on the other face however it is not real life accurate and causes more issues at render time.

Ah clear! But since there are two Harley logos on the sticker sheet amd several reviews mention that the sticker can be applied on both sides of the part, I thought it literally missed a sticker.

Oh sorry, I thought I only saw one in the instruction sheet and I didn't look further lol