Well, presumably the confusion here arose because the problem you ran into is happening because of your Ubuntu version, as pointed out in the comments - the problem is that there is no package for your Ubuntu version in the repository yet. This is a very common problem. We have a canonical post about it: What can I do if a repository/PPA does not have a Release file?.
However, it's quite clear that you are asking why APT behaves in the way it does (the answer makes this even clearer, as is often the case) and that the example from your system should be taken as an arbitrary example. This is not a problem specific to a development version of Ubuntu and so should not be closed for that reason.
Also, the question is not "opinion based" (once again - those who think it is may observe that it has been answered in a largely objective manner with reference to the source code). Also note that questions like "isn't x a security risk?" can usually receive good answers based on expertise.
Currently your question is not in the close vote queue any more and may not be closed. If it does get closed, comment here and we will reopen it.
In general if one feels that one's question has been wrongly closed one can:
- edit it to make it clearer that the close reason does not apply
- post on meta to ask for a review
- if one has enough reputation, come to the Downboat chatroom and ask for help
- if one has enough reputation, vote to reopen the question
NB: while moderation, including close voting, is undertaken by the whole community, most people here understand "mods" to refer to elected moderators i.e. this bunch.