Idol Worship
No it is not same as polytheism as a belief but at the same time, in certain scenarios and considering the gravity of this sin, it may put person in the same list of polytheists. One scenario would be repeated actions of this sort which is an indicator of a person’s arrogance and this sort of arrogant behavior has effectively the same result as that of an unforgivable shirk. It is for the God to decide after considering the person’s knowledge, circumstances, reason, excuse etc. but it is not something that can be brushed off so easily by simply calling it a sin.