The literal basis of muqaddima is that which comes before:
وَالْمُقَدِّمَةُ مَأْخُوذَةٌ مِنْ مُقَدِّمَةِ الْجَيْشِ
The term muqaddima is taken from the vanguard of an army.
Just as an advance detachment precedes an army, an introduction precedes the principal discussion and prepares the reader for it.
The literal sense of 'preceding' does not itself show that every introduction is a constituent part of the science; classification depends on the material and its function.