If we're calling a spade a spade, then both San Francisco and Inter are replicas of Helvetica.

They're both literally just Helvetica modernized a bit to remove personality (like the curled end to an "R" or "a", or the downstroke of the "G"), and with spacing appropriate for screens rather than print.

Inter isn't any more derivative than San Francisco is -- they're both derivative.

Which itself is a replica of Akzidenz Grotesk.

Do you care to elaborate? I understand it might look similar in style, wouldn't call it a replica though, a lot of the fonts are similar. For example, maybe a detailed pixel to pixel comparison why it might be a replica?

It is not a replica, they are similar in style (they’re both neo-grotesk). Also the design of the letters can’t be copyrighted in the US, only the files (.otf, .ttf etc.) can.