I have spent some time making a hap-hazard mess of a list of missing cpus from the database, its not by all means comprehensive and my patience have worn out trying to search every intel processor lol, here's what I cataloged so far, may or may not come back and catalog the rest.
All of these from wikipedia's lists of amd ryzen and intel processors.
DESKTOP
AMD
Ryzen 3 PRO 2100GE
Ryzen 3 1200AF (Zen 2)
Ryzen 3 Pro 3200G
Ryzen 5 Pro 3400G
Ryzen 5 Pro 3350G
Ryzen 5 Pro 3350GE
Ryzen 5 3500 (OEM)
Ryzen 9 3900 (OEM)
Ryzen 5 Pro 5645
Ryzen 7 Pro 5845
Ryzen 9 Pro 5945
Ryzen 3 5100 (OEM)
Ryzen 3 5300GE (OEM)
Ryzen 5 5600GE (OEM)
Ryzen 7 5700 (OEM)
Ryzen 7 5700GE (OEM)
Ryzen 5 Pro 7645
Ryzen 7 Pro 7745
Ryzen 9 Pro 7945
Intel
Core 2 Duo E6800
Core 2 Extreme X7800
Core 2 Duo T5250
Core 2 Duo T5270
Core 2 Duo T5300
Core 2 Duo T5450
Core 2 Duo T5470
Core 2 Duo T5550
Core 2 Duo L7700
Core 2 Duo L7500
Core 2 Duo L7400
Core 2 Duo L7300
Core 2 Duo L7200
Core 2 Duo U7100
Core 2 Quad Q9000
Core 2 Quad Q9500
Core 2 Quad Q9505S
Core 2 Quad Q9700
Core 2 Quad Q9705
Celeron G470
Pentium G2140
Pentium G2120T
Pentium G2030
Pentium G2030T
i3 3250
i7 4790T
i5 4690S
i5 4690T
i5 4590T
i5 4460
i5 4460S
i5 4460T
I3 4370T
i3 4350T
i3 4340TE
i3 4330TE
i3 4170
i3 4170T
Pentium G3470
Pentium G3460T
Pentium G3440T
Pentium G3320TE
Pentium G3260
Pentium G3260T
Pentium G3240
Pentium G3240T
(sudden jump to skylake because lol)
i5 6500T
Celeron G3900T
Celeron G3900TE
Pentium G4400T
Pentium G4400TE
Pentium G4500T
i3 6098P
i3 6100T
i3 6300T
MOBILE
Ryzen 3 3250C/
Ryzen 3 3350U
Ryzen 5 3500C
Ryzen 5 3450U
Ryzen 7 3700C
Ryzen 5 4680U
Ryzen 7 4980U
Ryzen 5 5600HS
Ryzen 9 5980HX
Ryzen 9 5900HS
Ryzen 3 7440U
Ryzen 7 7540U
Ryzen Z1 (Non-Extreme)
INTEL
I7 4720HQ
i5 6300HQ
i5 6440HQ
i7 4610Y
i7 4578U
i7-4510U
Intel N6000
Intel N6005
Intel N5100
Intel N4505
Intel N4500
Intel N5105
Embedded
AMD
Ryzen V1404I
Ryzen V1500B
Ryzen V1780B
Ryzen V3C14
Ryzen V3C44
Ryzen V3C16
Ryzen V3C18l
Ryzen V3C48
Intel
i7 4701EQ
I7 4702EC
I7 4700EC
I5 4402EC
i5 4422E
Also found an oddity of two duplicate cpus with the same name
A lot of the unannounced, unlisted, and unreleased AMD chips aren't on the database because we lack any real information about them. Some haven't even been photographed anywhere, and some only exist in motherboard vendor CPU support lists with zero supporting evidence of existence. If I have more information than just base/boost, core count, and socket type I'll usually try to add the chips. To avoid making shit up to fill out a page I will usually ignore leaked chips that fail to appear online in any capacity. Wikipedia lists are all inclusive regardless of whether a chip actually exists; they only need a citation to somebody's article claiming to have seen one.
As for the old Intel stuff, yeah. There are holes. Intel has 17 variations of every single die and some that they sneak out as OEM only releases so they get missed. I add what I can when I find them. Intel also has chips that they refuse to acknowledge exist at all, but then appear 5-6 years after launch on eBay when the systems start getting scrapped.