So looking at something like this to recommend to builder:

https://www.fypononly.com/famoml10.html

But question is - can this be added into the old house on the brick that goes up to the gutter or is it a fairly involved process?

What was the decision to not match the detail on the original house?

I don’t know other than I think the architect was just trying to add some details for curb appeal? I’ve reached out to ask, but have not heard back.

And I like the moulding but I do think it might be odd to have it on half the house and not the other half. So now am thinking it might be nice to add it to the entire house. But maybe that’s just too much of an undertaking to add to brick on an existing house.

I would have the architect come up with the detail on how to do this on the existing house.

And then the builder can determine how much work it will take, and then you can decide whether it is worth it.

But if the older part of the house looks fine without it, I would probably not do it on the new addition either. There's nothing wrong with just matching the existing house. It is specified as painted to match the brick, not to contrast, so I am not sure what it is adding to the design visually.

Agreed. It’s white brick. I honestly had never noticed the gutter area and the lack of moulding on the original house before anyhow. Although the original house is pretty old and in need of some sprucing up on the exterior. So this might be a fun way to spruce it up.

I would assume that it would mean removing the gutters on the existing house and doing something to the roof so it overhangs the new moulding (since it has some thickness) rather than having water pour onto the moulding on the way to the gutter. Even if it's Fypon I think the top edge would need to be protected and you don't want water to get between the moulding and the brick.

Explain to your 'architect' your concern about the entire house being cohesive. Check their license with your state.

If you use a polyurethane moulding (e.g. Fypon), you would need a wood cleat as a backer to attach to - so cleat on the brick, then moulding. Realize that your 'K' style gutter ("ogee") has a profile design which is meant to emulate a crown, and with no overhang to a polyurethane crown those 2 profiles will be adjacent and probably overpowering, where the profile of the polyurethane will be lost visually. Unless this is an old southern plantation with balustraded railings and acorn pediments over the windows, choosing a simple profile or none at all might be better.

Building on what Tim (Charles Ross) said, it appears you have "shingle vents" specified (called out as "low profile roof vents," which could mean anything) to work with no eave overhang. First, verify you are ok with them, many people are not and for most they are a last ditch effort for venting (in this example they are installed higher than the drip edge):

The shinge vent spec is an assumption though, as it seems the architect is passing the buck there. As other alternatives, there are also specific fascia vents or dormer vent styles for low venting.

What may be better, is to forego a crown, and install a simple continuous linear soffit vent in the short overhang. That would provide the better attic venting. If CA, verify fire requirements for soffit venting.

Wouldn't surprise me if it is just a standard detail that he imported from another drawing. Regardless, show a photo of the old part of your house