Looks like the same car was spotted with a normal plate. Is it possible that 4B* series was still issued last year?
Yes, it is possible. Because, there are 21 places in South Moravia region where the plates are issued and every place must have some plates in stock (no matter, how many). This 4B4 7646 is from Brno, as you can see here
Brno still has big stock of US format, series 4B4 7486-4B4 8255, actually highest is 4B4 7901 + there is many times confusion in issuing US or square formats, so the highest 4B4 7901 can be older than this 4B4 7646.