That is the point of checking a Custom. The rule is stupid. If you tell them why, there wouldn't be a need for that rule.
They don't answer to us, they answer to Caliburn. Caliburn doesn't answer to us, nor Zise, nor Lawliet. They answer to Versuvio ("V"), the owner of this site. It is a private website that you are able to use for free. Since the power and authority of the mods are not given by the people, the people do not ultimately need to be answered to or have everything explained to them.
That being said, a majority of the Staff will explain things upon request if done nicely. They don't have to, but many of them will if they have the time to do so. With that, it is often the case that when the Staff do choose to provide a basic answer (such as 'similar tech already exists'), it isn't 'good enough' of an answer. To that I say: you are lucky you got an answer at all because they don't have to give a reason at all.
And if you think that's stupid, well, good for you. You choose to use the free services of a site which expresses their right to operate in the way in which they do. Be reasonable, and the Staff will be as reasonable as they can. Waltz in here like you think you own the place, and you reap what you sow, as you do not, in fact, own this website.
Life isn't fair, and to be honest, most places of business 'reserve the right to refuse service to anyone.' They may not always exercise that ability, but when they do, it is their right.
On-topic: At least you asked if it were possible and got an answer. It is very time consuming for a mod to try and sift through thousands of customs in order to find the exact one which is similar to your submission. It's the unfortunate truth. If you think they are in error, feel free to sift through every custom one by one to make sure, but it won't really change things as anyone can say "i read tge whole thing and didn't find anything close to mine" without actually reading through the threads. :/