Odd answers may be due to the history of this stuff (one of the problems with web searches is that they can easily turn up out of date information).
Verizon used CDMA technology for its 2G network, and derivatives of that for its 3G. Those technologies don't use SIM cards, so for a long time you had to register a phone with Verizon in order to use it on their network (which of course meant that VZW could choose whether to allow you to do this or not). But the 4G technology, LTE, is based on the GSM standard, which is where the SIM card came in, and the whole point of the SIM is to allow you to move your connection to a different handset by swapping the SIM card. And my understanding (mainly from VZW customers in this forum, since being European I have never had a Verizon account) is that Verizon have not done anything to stop you doing this. But the fact that for many years you could swap SIMs with other networks but not with Verizon (or other CDMA carriers) might be the reason why you found mixed answers in your searches.
