In real situation. Taiwan aircraft registration number format is B-12345 not B-1234. Please kindly verify. Thanks.
Most countries use a X-XXXX or XX-XXX format, and China uses B-1234, so they may have just left Taiwan the same as China. Don't forget that this is a game based on real life, not actually real life. If Taiwan using the same registration as China is a sensitive issue for you, perhaps try sending the game devs a polite message about it. This game is updated on a regular basis.
Thanks for your kind reply. I just try to make the game one step more closer to real. They did so for a good job. It is not big issue to change a registration format. I will try to write to game team.
Taiwan Reg starts from B-00001 to B-99999 (Except B-1500 to B-9999 which are for People's Republic of China)
Full list of prefixes can be found https://en.wikipedia.org/wiki/List_of_aircraft_registration_prefixes (https://en.wikipedia.org/wiki/List_of_aircraft_registration_prefixes)