Direct answer
CR2012 and CR2016 share 20 mm diameter, 3 V nominal voltage and lithium manganese-dioxide chemistry. Their heights are 1.2 mm and 1.6 mm, so the 0.4 mm physical difference prevents an exact-size verdict.
Both are 20 mm in diameter; heights are 1.2 mm and 1.6 mm. The physical envelopes differ (20 × 1.2 mm versus 20 × 1.6 mm). Do not force, stack or infer equivalence from a shared diameter or code pattern.
Do not infer acceptability from fit alone. The device maker’s complete code and current instructions remain authoritative.