coffee taste varies due to dozens of factors
Coffee is an agricultural crop and depends on variable conditions of climate (e.g.: rainfall, sunlight, temperature, humidity, wind, el Nino), altitude, soil composition, soil amendments and input fertilizers (type, quantity and timing), pest management, disease control, orchard pruning techniques, tree species, tree varietals, age and health of trees, shade tree management, picking (standards, method, ripeness), processing methods, grading standards, freshness and quality management.
I certainly omitted some factors and many overwhelming details...so you can extrapolate the sum total of annual change potential when each of these factors plays a role in cup characteristics.
Two different lots of coffee from the SAME FARM and THIS crop year can easily have measurably different quality and cup characteristics. Therefore two different crop years and coffees from different growers within the same country of origin are more likely different than identical. These are some of the reasons that coffee agriculture, processing, green coffee buying, roasting, blending and quality management are such highly skilled professions.