Often when you have to qualify something (intellectual property instead of just property), it's because it's used as a metaphor instead of a subcategory. Intellectual property is a form of property as much as political science is a form of science.
You can metaphorically say it's theft, but it doesn't manifest as theft of actual property.
For example: many people (myself included) have downloaded the $1.000.000 torrent (a list of files whose value amounts to a million dollars). I found nothing of use in it so I just deleted it. Did I cause a million dollars in damages? Was the damage restored when I deleted it?
If you consider the same for actual property there's no question about it. Stealing a Bugatti does cause millions to be lost, and destroying it makes it irrecoverable.
Edit: to be clear, I agree it's not 'theft', but am pushing back on the way this distinction is sometimes used to insinuate that it is victimless (not saying the poster above is claiming that, just that it's worth pointing out)