Multitasking is better than just learning one skill at RuneScape Mobile gold one time. Arguments that only one skill should be taught at any given time will likely also be made by Alch at banks, who ask why this is so boring. Either that, or they believe that training several abilities at the same time is, for example fishing, and then using the resulting fish to cook.
It is not against the rules or even against the "spirit of the game" to train efficiently by training multiple abilities at the same time like Bolt fletching. Zarfot was once well-known for his ability to master all the skills and received 200M Fletching using this method.
It is impossible to learn another skill while doing other things. Alching is close however it needs the Standard spellbook (i.e. There is no Ourania Teleport and no casting in Monkey Form. The casting time is very slow (MUCH more so than Bolt's fletching), and it requires constant switching to the Spellbook tab.
Jagex, which is next on your list? Superheat-All? Clean-All herbs in a 1 tick limit Is AlchX available? If it's not broken, fix it until it fails. What is the solution to this problem? It's very simple to switch between Manual and Automatic for cheap OSRS gold certain skilling that require repeated clicking. Some players prefer slower XP, while others prefer to work harder.