Here's a little more info. The bits in bold about the SLA are not in the "Apollo 11 Spacecraft History" at Apollo by the Numbers
https://history.nasa.gov/SP-4029/contents.htmThe list is about the 16mm silent film on the first part of Disc 1 of the Apollo 11 original 3-DVD set from Spacecraft Films, and there might be more tucked away on the Mighty Saturns sets. The current Apollo 11 set might have more too.
http://www.spacecraftfilms.comMaking Ready 16mm film — No audio0 - 01:33 S-IVB Checkout — 21 Jan 1969
0 - 03:32 S-II on Dock — S-II Stage Arrival — 6 Feb 1969
0 - 05:28 S-IC on Dock — S-IC Stage Arrival — 20 Feb 1969
0 - 04:51 S-IC Erection — 21 Feb 1969
0 - 01:57 S-IVB Mate — S-IVB Aft Skirt Mating — Date Unknown
0 - 05:34 S-II Erection — 4 Mar 1969
0 - 02:55 IU Erection — Instrument Unit Erection — 5 Mar 1969
0 - 05:45 S-IVB Erection — 5 Mar 1969
0 - 03:05 CSM Checkout — 1 Apr 1969
0 - 03:29 LM to SLA — LM Installation into SLA — 4 Apr 1969 (some frame jitter)
0 - 06:33 CSM to SLA — CSM Installing in SLA — 10 Apr 19690 - 04:33 S/C Erection — Spacecraft Transfer and Erection — 14 Apr 1969
0 - 08:34 Rollout — 20 May 1969
0 - 11:15 Pad 39A — Work at Pad CDDT — 1 Jul 1969
So the LM and CSM were installed in the SLA by 10 Apr 1969 and there's 10 minutes of film about it on the DVD. Perhaps a month before Rollout and three months before launch was sufficient time to get those wrappings off.
Others oldies who were around at the time will possibly remember the fears some laypeople had about what Earth germs might do to the Moon, and even worse, what Moon germs might do to
us. So I wonder if those external wrappings got some special visual treatment for the public's benefit, the same as a few other procedures did.