In 2014 I spent 40 days during Ramadan in Mardan. For the first time in my life, I saw imams reciting short suras and finishing taraweeh in almost half an hour. I asked an alim there about finishing quran in tarawih. He said that finishing quran is a separate Sunnah and offering 20 rakaats is a separate sunnah. I think the ulema in other parts of the country and world also know this but they are reciting full quran out of pressure of awaam because the majority doesn't know the proper rulings of Tarawih.