The H1-B is a dual intent status. There are categories that are strictly non-immigrant intent, TN work permits fit this category. Border guards can and do test that you have non-immigrant intent during normal border crossings while under this status ("Where is your home?" "what will you do once your TN is over?").
If it really was intended that H1-Bs not have immigrant intent then there was a legal framework already in place to ensure that. Most likely it is you that is incorrect about the purpose of these H1-Bs.
The "dual-purpose" nature of the H-1B basically means that (1) you are not prohibited to enter on an H-1B with the intent to stay permanently, and, perhaps more significantly (2) you aren't required to leave the US for a period of time after entering on an H-1B before getting an immigrant visa which will let you stay permanently.
But it is still a non-immigrant visa that does not lead to permanent residency or citizenship, but requires you to qualify for, apply for, and secure an immigrant visa if and when you want to become an immigrant rather than a non-immigrant worker.
If it really was intended that H1-Bs not have immigrant intent then there was a legal framework already in place to ensure that. Most likely it is you that is incorrect about the purpose of these H1-Bs.