This was discussed in a Debian bug report: #435715
Remove window resize from 'putty':
The escape code (CSI ? 3 l) sets 80-column mode, forcing a window
resize. This is not appropriate for a reset sequence.
which was inconclusive because PuTTY's developers did not participate:
It seems there was nothing from the putty developers so we will keep
this terminfo line the same.
The relevant documentation for the reset-strings is in
Most initialization is done with
is2. Special terminal
modes can be set up without duplicating strings by putting
the common sequences in
is2 and special cases in
A set of sequences that does a harder reset from a totally
unknown state can be given as
rs3, analogous to
is3 respectively. These
strings are output by the
reset program, which is used
when the terminal gets into a wedged state. Commands are
normally placed in
rf only if they produce annoying effects on the screen and are not necessary
when logging in. For example, the command to set the
vt100 into 80-column mode would normally be part of
but it causes an annoying glitch of the screen and is not
normally needed since the terminal is usually already in
80 column mode.
Because this is a matter of taste rather than an error, and because one of PuTTY's developers chose to use this method for resetting the terminal (and none of the others participated in the subsequent discussion), there was no reason to change the initialization style.