Engaged or married ladies

So we’ve been talking about marriage. He asked me last night what ring size and I told him that we should go shopping so I can show him what style I want. Like I’m not picky but there is a style that I like and since I have to wear it forever, I think I should be able to at least show him my ring style. He told me it doesn’t work like that and engagements are supposed to be a surprise. I told him that no matter how much engagements look like a complete surprise on camera, it never really is. Women will go ring shopping so their men will know what ring to pick in the coming months. Please ladies who are engaged or married... is this how it works?