No, this isn't an EACA, and the plan document does not allow only the "net" match to be made.
I think it's common for a platform vendor to have a deposit tagged to a certain plan year, and it's becoming more frequent that they are using that information to limit transactions under the idea of trying to prevent errors. YMMV on how useful that is. A couple of years ago, I had a sole prop who deposited $10K in deferrals in January for himself for the prior year but he coded it in the current year. When he went to make his full deferral deposit for the current year in the current year, the platform blocked it because it was counting that prior year's receivable and it flagged him as going over the limit. It took way too much effort to get that first deposit changed. But I can see how they are trying to "help".
I think we've all had this happen once or twice; luckily that is not the situation here.
I think this is a good takeaway - while they give you a miles-long contract, hopefully, it specifies things like this so you can know what to expect.