This ordering, however, has the effect of suggesting an initial positioning of subordinate clauses that is more frequent than usual.

[diamondcutter]

In the following examples we seek to demonstrate correspondences between coordination and subordination, while preserving the information ordering. This ordering, however, has the effect of suggesting an initial positioning of subordinate clauses that is more frequent than usual.
Source: A Comprehensive Grammar of the English Language by Randolph Quirk, Sidney Greenbaum, Geoffrey Leech.

Does the second sentence mean it’s more common for subordinate clauses to be initially placed?

 

[Lycidas]

In the following examples we seek to demonstrate correspondences between coordination and subordination, while preserving the information ordering. This ordering, however, has the effect of suggesting an initial positioning of subordinate clauses that is more frequent than usual.
Source: A Comprehensive Grammar of the English Language by Randolph Quirk, Sidney Greenbaum, Geoffrey Leech.

Does the second sentence mean it’s more common for subordinate clauses to be initially placed?

No, it means that the sentence-initial placement of subordinate clauses is less common than those examples, which use that placement, might seem to suggest it is.

The sentence-initial placement of the subordinate clauses in those examples should not be taken to imply that's where subordinate clauses are most commonly placed.