Are non-adepts guaranteed by any means?? The adepts are guaranteed by platinum gm completions... and I get the sense that farming gms is better than focusing. Perhaps this will be true of non-adepts. If the cipher cap would be removed, that would help... but you're right, it does seem like unnecessary restrictions as things stand.

I was surprised when I read that it would only cost one Engram and one Cipher for focusing, until I saw that it was only for the weekly non-Adept and immediately lost interest. Now that you mention it, that is extremely weird to require them for non-Adepts when the only reliable resource for Nightfall Ciphers is Grandmaster Nightfalls when the non-Adept drops from any Nightfall. Hopefully they either drop regularly from all Nightfalls or they consider some other means because it doesn't make sense otherwise. This Economy team has been making a lot of rather poor decisions to be honest, from some focusing taking 5 whole Engrams to removal of Legendary Shards.

So this is what xur has been selling them one in a while

As it reads, yes, but I'm assuming there was a missed note, either that ciphers will be dropping from regular nightfalls or that they'll be added to other sources like they did with the Coil. The other side is this is their way of reducing access to them so players that want to farm specific weapons will wait for that week and then farm platinum masters/GMs.