Nonsense. It was never 80%. Each
district, not just province, has a fixed quota of seats in all branches of the Army. The reason behind the dominance of recruits from Punjab (which weren't all Punjabi) in the army was due to the lack of applicants from other regions. The Army remedied this by reducing the educational and medical criteria (compared to Punjab) for the applicants from the less represented regions, including Sindh. It also provided waivers for them. By 2005 Punjab's share had already reduced to 43%, less than its population percentage. Bet that particular someone didn't mention that.
https://www.globalsecurity.org/military/world/pakistan/army.htm
Do you see now how ethnic garbage is created and spread in this country?
I'm sorry but CSS recruits on straightforward merit which is made public every single time, it's very transparent. It is also run by the Federal Public Service Commission i.e. the bureaucracy, not the provincial government. Karachi's share is under Urban Sindh's 40% quota and it does receive it in full but does not avail it fully due to a lack of qualifying candidates, neither does Rural Sindh. The numbers are available for every year. PPP and Sindh's provincial government cannot do anything about it.
I am illiterate on the provincial departments of Sindh, so you obviously know better than I.