I mean, yes, but when you read the inclusions for the study you can see how they set it up to get the desired results.

We identified 1,226 index cases over the study period based on the
inclusion criteria of having a positive SARS-CoV-2 diagnostic test
(without a prior positive test in the preceding 90 days), continuous
incarceration beginning before 1 April 2020 (to ensure reliable
reporting of prior SARS-CoV-2 infection) and a valid close contact in a
shared, closed-door cell (Figs. 1 and 2 and Supplementary Fig. 1).
We defined close contacts of the index case as residents who shared a
cell with an index case for at least one night while the index case was
infectious (assuming a 5-day infectious period after a positive test22);
we required the close contact to have a negative SARS-CoV-2 test within
2 days of first exposure as well as follow-up testing data within
14 days after last exposure (64% of close contacts met both criteria).
Each index case was assigned a single close contact at random if
multiple contacts were identified (<0.1% of cases). Further
description of inclusion and exclusion criteria that were needed to
address concerns for confounding and misclassification is available in
the Methods.