You're overthinking this, there isn't a decoder wheel. The scheme is evolving and not entirely rational. Applying too much logic here will just give you a headache.
L0 is a family of parts. Low-Power is a bit of a loaded term, depends what you're comparing it too, but usually means there isn't a separate battery input.
The data sheets I think have some details of the decomposition, the part number, ie 053 is somewhat arbitrarily chosen by ST. The R8 field here typically defines the memory configuration for RAM/FLASH with a specific family, and the packaging. R=64-pin, 8=64K FLASH, with perhaps 8 or 20KB RAM
Parts with a number 10 higher tend to indicate presence of Crypto/Hash units, be the odd/even numbering there is not consistent.
