Okay I'm confused, a normal state BTW.
The reason I shoot 400 film is to be able to shoot at 400 (or more) not 250.
The issue here is that the mfr says the film is 400, but if you look at the fine print, they also say that their published ISO is only a starting point and that you are responsible to determine the actual ISO that works for you. They aren't going to be responsible for your results, and want you to know it. You might sue them. In fact, the film you believe to be "400" may actually be "250" in the way you use it. Or it could be "400". Sometimes, but seldom, the rated ISO actually works. Generally, it isn't enough, in my experience.
Your "(or more)" is sort of interesting to me. Why would it not be a problem for you to increase the ISO but would be a problem to decrease it? The working ISO is hopefully not a guess and by gosh sort of thing. If you don't give enough exposure, you drop your shadows. That's the law. The notion of "pushing" film is a sort of a lottery, generally. If you want to get the maximum speed out of the film you are using, it is really important to understand the practical threshold and the response curve for your own materials. Without it, you are flying blind.
A lot of what we read gives the impression that we can just pick any old ISO (always higher, never lower) and just develop more to make it come out ok. If my livelihood were to depend upon the quality of my exposures, I'd be very careful about this.
I test. It can be boring, sometimes, but it saves LOTS of time, money, and disappointment.

