Why Oscar Piastri avoids Singapore GP grid penalty after Baku disaster

Oscar Piastri will not face a grid penalty for the Singapore Grand
Prix, despite being unable to serve a punishment in Baku.  The
championship leader was handed a five-second time penalty in the
Azerbaijan Grand Prix for jumping the start, as was Aston Martin's
Fernando Alonso.  However, the McLaren driver was unable to serve
his penalty after crashing out on the first lap. Piastri made a
huge error at Turn 5, causing him to crash into the barrier on the
outside of the corner.  The Australian was forced to watch the race
from where he crashed, due to being unable to cross the Baku City
Circuit to return to the F1 paddock.  Piastri being unable to serve
his penalty immediately led to speculation that he could receive a
grid penalty in Singapore; however, that is not the case following
a recent rule change.  In the past, a driver has received a
three-place grid penalty for being unable to serve a five-second
time penalty, although that rule has changed.  The teams decided
last year that five-second time penalties should not be carried
over if they cannot be served due to a retirement, unlike a
10-second time penalty or multiple five-second penalties.  This is
outlined on page 13, note eight in the F1 penalty guidelines, which
states: "In cases where there is a single five-second penalty which
a driver is unable to serve due to retirement, the Stewards will
not convert that into a grid penalty for  a subsequent race. 
"However, if there is more than one penalty, the Stewards may
convert the 5s (and other) penalties into a grid penalty."