pr: flags -T and -s behave differently than in GNU pr

Test case: transposing a simple table.
Input data (in.csv):

A,1,2,3
B,1,2,3
C,1,2,3

Used command:

<in.csv tr , \\n | pr -3Ts,

Expected output:

A,B,C
1,1,1
2,2,2
3,3,3

Works as expected with GNU pr 9.5.

The output of uutils pr -3 -FTs,

A                      ,B                      ,C
1                      ,1                      ,1
2                      ,2                      ,2
3                      ,3                      ,3

Differences:

• uutils pr requires number of columns to be specified separately: pr -3 -Ts, otherwise, the following flags don't get processed;
• for -T to work, it requires -F as well: pr -3 -FTs,, otherwise, -T doesn't work;
• columns get aligned unconditionally, even when -s, is specified. No difference between -s, and -S,. In GNU pr, the columns only get aligned with the -S flag.

Start with the uutils pr command and reproduce the provided in.csv case using the listed flag combinations, comparing results with GNU pr. Trace option parsing and column formatting for -3, -T, -s, -S, and -F; done means the relevant combinations match GNU behavior and the transposed output is unpadded for -s.