I was fortunate to arrive on US soil in 1975, and for the initial years without any Vietnamese restaurant anywhere in North America, we all made pho ourselves at home using the best ingredients we could find at Chinese and American markets. As you can imagine, not all ingredients were available. We drove many miles to find a bottle of nuoc mam (fish sauce) that didn't even remotely resemble Viet fish sauce, but that was what we use. And guess what? Many of us never made pho in Vietnam.

So I'm skeptical of all these people claiming family hand-down pho recipes. It's all made up marketing attempts to sell you their pho.

• It's rare that people actually make pho at home in Vietnam. Those who do may have special ways or ingredients to cook their pho. But whatever they do is highly dependent on their own economic and personal tastes, and highly unlikely to be scalable to restaurant volume and consistency. Even if they are able to scale such recipe to restaurant volume production level, what they end up with is probably no longer the actual original "family" recipe.
• It may be true that more Vietnamese people make pho at home in the U.S. However whatever recipe they use for home cooking are again highly tailored to personal taste or the taste of a few family members. If they are able to open a pho restaurant then such home recipe still needs to be scaled up to restaurant level production, and having to make changes to the recipe is inevitable.

So going from home cooking to restaurant cooking itself will require a change in recipe. It may be more accurate for a restaurateur to say "my pho recipe is based on my mother's recipe" than to say "I use only my mother's recipe". But then again, what recipe is NOT based on something already existing?

So the question becomes "where is the line that you consider two recipes to be the same, or put it another way, where they are no longer the same", in the context of restaurateurs saying they use handed down family recipes.

The bottom line is I think it's all part of the Halo Effect, the subconscious process in which we jump to a conclusion based solely on our impression of a word used, a person, label, or company. This is rampant especially in the food industry and anywhere else where a seller wants to sell something.