It's really all about supply. Yes, if you have a really robust supply or a frank oversupply, you can get away with fewer feedings in 24 hours. And there are working mothers who sleep more than 5 hours at a time. I am occasionally one of them (when my LO sleeps a longer stretch, which she does not consistently do!). But I also have an oversupply - I am still freezing 6 - 12 ounces of milk every day. So I can get away with it. But supply differs wildly from mom to mom. Some struggle to keep up, others have more milk than they know what to do with and have to actively decrease supply. So just because some mothers can do it, doesn't mean that your body will respond in the same way. You mentioned in your first post that you've had some supply problems. So you want to really guard that supply. And supply can be all the harder to keep up if you are relying on pumping at work during a big stretch of the day. Because if baby is sleeping a long stretch and night and you're at work during the day, that doesn't leave many nursing sessions. Which is why I think you've been getting the advice not to drop that feed.
Also, agree with djs.mom that the number is 24-32 ounces/24 hours for a 9 month old. Milk needs are stable up to a year, then gradually solids start to increase and milk needs start to decrease.