Is it plagiarism to copy formulations from others? As a non-native speaker of english, I often struggle with always finding new, well-sounding, non-repetitive descriptions for the same thing and I also, to be honest, find it a waste of time of always having to do something different. For example:

Section 1 describes the X while section 2 is about the Y.
The Z is explained in section 3 and section 4 refers to A. The next section is about B...

Is it ok to just copy the formulation of someone else (of course my X,Y,Z,... are completely different) and always use the same thing?
Sentence patterns are not intellectual property; otherwise, every author who wrote "To X or not to X" would be plagiarizing Shakespeare. (They are "riffing" off of him, but not plagiarizing!)

The example you are citing is perfectly innocuous, particularly since you are not doing anything more than summarizing the paper contents. The only thing that would make it wrong would be to copy those sentences directly from someone else's work.