It's certainly not true that "anyone with good internal" can do it. It's actually a technique.
Simply because you have strong internal does not mean that you can do it well. It's still the application of the martial art and usage of qi.
To see an example of extreme internal energy, but poor technique, see Shi Potian.
Anyone else surprised that PJ still hasn't mentioned the Song Dynasty level feats of 19th century era Linked Cities?
In my opinion, martial arts in JYverse isn't a complete downward trend. There are ups and there are downs. For example, there is a clear decrease in level between BXJ and DOMD and a even bigger decrease between DOMD and FFSM. However, things picked up a bit in Linked Cities, taking place in late Qing. Also, things also seemed to pick up a bit in the late Ming with SPW and OTG. The feats of Linked Cities, SPW, and OTG aren't obviously weaker than those of the Song and Yuan Dynasties despite taking place hundreds of years later. However, the feats of BXJ, DOMD, and FFSM show obvious decrease in level. It's not an absolute downward trend.
A Deadly Secret (Linked Cities) has some impressive feats, such as Voice Transmission over a distance of 5+ Chinese miles, resurrecting people after they'd stopped breathing, and launching 36 attacks in the blink of an eye. However, the overall martial arts description is still weaker than Ming dynasty.
忽见柳荫下两个小孩子在哀哀痛哭,瞧模样正是武敦儒、武修文兄弟。郭芙大声叫道:「喂,你们在干甚麽?」武 修文回头见是郭芙,哭道:「我们在哭,你不见麽?」