They're absolutely different. IP rights are a creating of artificial scarcity for what would otherwise be an infinitely-copyable work. Physical property rights are a codification of rights to a naturally scarce item.

IP rights require specific limitations on speech for everyone who is not the owner of an IP. It's walling off some expression as "copyrighted" so that no one other than the "owner" can express them (in a commercial way at least). Compare this to traditional property rights that merely prevent you from walking up to the owner and taking their (non copyable stuff) - a much lesser restriction.

This is why IP rights need to have limitations like a time limit, but I don't see why other limits like non-transferability are out of the question.

It's very simple if you spend more than 12 seconds thinking about it. Non-transferability devalues the property you're trying to sell.

Why is that so hard to understand? You're free to negotiate such terms, but the buyer can and will push back.