NO, you are completely wrong. First off the second number was never about the number of cores or threads, your own examples are wrong, the 1300X and 2300X are 4/4 CPUs, not 4/8, then you forget about the Ryzen 3 3100 that is a 4/8 CPU.
Also who said that you cant have a 4/8 4200G when you have a 4/4 3200G??, that is called PROGESS, the 2nd number was never about cores/threads, it is used to indicate what SKU is better than the other in the same generation, thats it.
What you cant have is a $140 4200G and a $220 4400G because everyone will notice what you are doing.
and finally, there is nothing wrong with the 4400G naming considering these APU will share naming with the Zen3 CPU, the problem only happens when you want to have a 4400G that is more expensive than a 4600X. The 4400 indicates that is the lowest of the Ryzens 5, and would be correct.