I would doubt that it really results in lost orders as people have already invested a lot of time by selecting their food choice and by that time are hungry.
Not everyone will understand that the problem is related to their autofill not behaving properly - it's not too far fetched to think that after trying to submit a few times, that someone would abandon their efforts because the "site isn't working". Probably not as high of a lost revenue as proposed, but I wouldn't doubt it leading to some lost orders.
Some 25 years of web usability research has taught us that users are incredibly impatient and will bust out of conversion funnels over the tiniest obstacles like they are the Kool-Aid Man on crack. The conversion rate for most restaurants (e.g. customer places an order) is only 1-3% [0,1].
I mean, that it will result in lost orders is almost a fact due to the sheer number of transactions. At scale, all possible events will happpen. So with that in mind the author of the post said he thinks a conservative number is 0.5%. Maybe you think that's lower. The author posited that option and asked how low do you think it can go to make it worth it to fix the form?
Or to put it another way. Estimate how many programmer-hours it takes to fix this issue. With that number calculate the % of people that are likely to abandon the order. Is that % likely to be happening?