Even if this were true, which I don't think it would be because I don't assume the conditions today would exist then, you'd still have teams that would have more flexibility to deal then now. Vegas isn't going to give you a player off their roster at the deadline, no contending team is, but in the summer it's more flexible.
As a rule of thumb I always think its a mistake to trade players like Hanifin at the deadline. Should always deal higher end pieces like that in the summer to increase your suitors.