Looks like I'm getting somewhere. I figured that it would always cache upon first request and thus show "Age: 0". However, that doesn't seem to be the case.
wainfodecode "[V2.S10202.A34484.P65790.N13710.RN0.U1555833138].[OT/html.OG/pages].[P/0.1].[O/0.2].[EH8/20].[DH1/0].[C/Mk.0].[K/n]"
V2: X-WA-Info Format Version
S10202: Response was served from the origin web server, because the cached content had expired.
A34484: Application: /Common/www.domain.com_aam_custom
P65790: Local-policy: /Common/www.domain.com_custom
N13710: Request Policy Node: Pages
RN0: Response match did not supersede request match
UCI hash: 5cbc2132
Object type: html
Object group: pages
Request served from TMM: 0.1
Request owned by TMM: 0.2
Entity hit count (local/remote): 8/20
Document hit count (local/remote): 1/0
Document in memory/small object cache.
Reason: Usable content received.
Bypass: Not applicable.
Parking: Not parked.