sssd front-end, AD back-end.    Does sssd use initgroups to use initial group membership?

I was recently debugging a sssd connection problem in the /var/log/sssd/sssd* logs (debug level 9).  and I thought I saw a reference to initgroups.  or getgrouplist(). 

my /etc/nsswitch.conf file has:

  passwd:  files systemd sss

  group:  files systemd sss

Should I also have a line with:

  initgroups:  files systemd sss

Spike White