Hi there, OP !
Doing some more thinking. Wanting to consider the meaning, when a 2-state device, like any typical pivot lever or sliding thingy gets involved, where the machine itself isn't considered to be in BINARY realm, (such as previous example running as a decimal device and decimal BUS for data transfers. I think the fuller description has to be something along the lines of 'Binary Coded' numbers. Otherwise, any device having an obvious physical set of two stable states of position could force folks to admit, perhaps incorrectly, that some system is binary based.
But that's somewhat imperfect, when a single bit is (often) processed as, yes, 'BINARY'. So;...round and round we go.
I'd suggest, maybe a more nuanced approach, to 'tiptoe past' the 2-position things as being (sole) proof. Otherwise every open/closed door, eyelash, birth twins, and other 'things of two's in a set, would trigger a legitimate 'binary System' label.
Having said that, the OP's question included OCTAL, and DECIMAL based systems. In those two types, definitely binary, the OCTAL variation uses 3 bits, in binary code, using all eight states, (0 thru 7).
The BCD types simply use just the first 10 states, usually ignoring the (10 thru 15) binary states available, to create a system that has decimal based behavior, and, on lowest function level, binary based hardware.
Another system type is ASCII, for encoding a character set, using 7 of the available bits, (in a system byte), where I believe there are 96 distinct states used for characters, again ignoring states from 97 through 127. Those, of course, are useful when encoding various punctuation symbols.
So, that language could refer to a 'base 96' system, incorrect language as the 'base' is still base 2, or binary based.
Somewhat of a matter of language, but I tend to consider a binary coded decimal system as having BOTH types, in a hierarchy,...not definitely correct. Similarly, if you had a BCD system using two digits (BUS), then I like to refer to
'Base 100', the most correct phrase is 'Modulo 100', as a programmer would think of the BUS and memory formats. It's more of being 'virtual base100' in those cases.
Twisted language, but once you've used the 'virtual' term....gets dicey but survivable..