The automobile market is not like smartphones. In spite of assembly lines, the identical unit is not stamped out one million times and sealed in glue.
Car designs are quite modular and individual components and suppliers are revised during manufacture. There are far more intermediate sub-assembly steps and smaller volumes produced in each batch. It is common to see recalls and technical service bulletins that "patch" cars already delivered to gain some of the fixes devised after the car left the line. Sometimes these are direct replacements of parts,and sometimes they are literal patches of the older design, such as applying an extra gasket or some adhesive to resolve a rattle in an interior trim piece which was designed away in its next revision.
While marketing maintains "model years" as a nominally uniform offering of a particular car, it is not uncommon to find odd half-year or worse hybrids which mix together cosmetic and mechanical features of different years. These happen when the manufacturer drains out certain supply chains and integrates unusual combinations of the different modules into specific cars. People focus on the visible parts like cosmetic body trim or interior features, but this also applies to mechanical and electronic parts buried deep inside the car.
No, because that doesn’t affect the customer. Tesla’s most loyal and gung-ho customers are punished for their enthusiasm by getting the worst Model 3s that will ever be made.
It’s like apple, every year iphone is the best iohone yet, but that doesn’t imply directly that the previous model was bad.