I would bet though the heat cycling the cast iron vs Epoxy in an exhaust port the coefficients are not the same and would loosen.
Indy Cylinder heads used to do cast iron repair.

For repairs in exh ports of blocking off exh crossovers there’s a ceramic epoxy just for that type of work.

I know some new head are found so it is not really an issue fixing these anymore. But, I frequently weld iron heads and use epoxy on heads. Looking at those pictures of the problem area you could definitely have added epoxy and ran it. Bolzona or Resibond are probably the best IMHO. Followed by Splash Zone, then Moroso A-B. JBweld is ok for some stuff. Splash zone was out of stock last time tried to ordered it. If you want to never have an issue with epoxy use to Evans waterless coolant.

There is plenty of room for epoxy there on that spot in the bowl. I would actually epoxy all the ports in that area, (Steve25 said it also on a earlier post). Most times I ported and intake like that I lost flow. There is no reason to cut the bowl down that deep.

If the port gets extremely thin I will weld and use epoxy. This Resibond is what I use on the exhaust side.

Resbond 907GF is what I use for exhaust work. heat rating…2350*F

all good points hopefully someone can use this info in the future! Thanks all for commenting with solutions.

Also, I don’t think it was mentioned, but if you are using Ethanol, it can lift Splash Zone, Moroso a&b, or JBweld. For E15, and even E10, they need covered with a urethane paint to protect them. Belzona 1111 is more resistant to ethanol and antifreeze than those, and doesn’t require anything special to protect it. It is more expensive though.

Yes, and Balzona is expensive but welding or brazing is far more expensive!

Depending on where your welding or brazing localized heat if near a valve guide can sift it when cool.

So now your into not just the cost of the welding, but a new valve guide and in all likelihood a touch up valve job.