I've heard this and similar concerns from employees of multinationals who meet someone while at an overseas branch. They want to do what they can to avoid snags.
I probably should have listened to her.. I did it the "right" way since I wanted to quit that job anyway. Got married abroad and filed an I-130. It took like 18 months to get it, it was nuts. I'm a native-born US citizen and my wife is from Japan, no criminal records or anything, and I was making 3-5x the national median household income this whole time, so it's not like there was anything tricky about our case.
I'd recommend you just talk to a lawyer. I hired a lawyer for our case, and it was about $3k total. It would've been entirely doable without the lawyer's help, but it was easier that way and I helped fund her charity work where she helps refugees and domestic abuse victims.
It is very much a problem if your partner is deemed to have entered the US under false pretenses. That is, if they enter the US on a tourist visa and then you get married and they apply for a change of status, immigration can look askance at your spouse -- "The original tourist visa was a lie, you always intended to get married and change status, they are now barred from the US for 10 years." It might be faster, but you don't want to run that risk, even if the probability of that happening is low.
Wish we would have had an overwhelming urge to get married when we were visiting my family in the states instead.
> With your visa, you can apply for a single admission at a U.S. port-of-entry within the validity of the visa, which will be a maximum of 6 months from the date of issuance. You must marry your U.S. citizen fiancé(e) within 90 days of your entry into the United States.
Source: https://travel.state.gov/content/travel/en/us-visas/immigrat...