Hen here from PCSG. Thank you for the hint and your evaluation. 👍

Similarly, will there be a problem for text/javascript ?

no there is no problem. the part comes directly from the core. 99% of the template designers use the quiqqer header. those who don't use it, need to know exactly what they are doing.

the thing is, there are more things in the template header, like meta specifications, title etc. so this is a general template specification for template designers.