Thinking about it, I think the Seagate manual stating Perpendicular is referencing the reserved CMR section that most SMR drives have. This makes sense since the manual states the ST5000LM000 has five platters. So it would be five, 1TB platters of which a portion is CMR.

This also makes sense of the manual listing ST5000LM024 as having either four or five platters. Either four, 1TB platters with reserve CMR sectors or five, 800 SMR platters without the reserve.

There’s a bit of mystery around these drives.

TL;DR: It’s extremely hit and miss on which of these drives had (if ever) CMR/PMR platters. There seems to have been a time in the mid-2010s when Seagate was using Samsung technology in some of their drives. So finding which drives definitely did (if ever) had CMR/PMR platters is extremely difficult.

The Hard Drive Platter Database says the ST4000LM024 and ST5000LM000 are SMR.

BarraCuda (5526RPM, 128MB cache, SATA-600 interface, Advanced Format, Shingled Magnetic Recording, 15mm z-height)

ST4000LM024 4TB (4/8)*

ST5000LM000 5TB (5/10)

*Note: The manual suggests there may be 10-headed versions of this model floating around.

https://rml527.blogspot.com/2010/09/hdd-platter-database-seagate-25.html

And so does the the Seagate Datasheet dated May 2020

https://www.seagate.com/content/dam/seagate/migrated-assets/www-content/datasheets/pdfs/barracuda-2-5-DS1907-3-2005US-en_US.pdf

However, their Sep 2020 product manual says Perpendicular. Page 10

In addition, the blog states the ST4000LM016 uses 800GB platters.

800GB/platter Section (all drives under here use platters that can hold 800GB of data apiece.)

SpinPoint M10P / Seagate Laptop HDD (5400RPM, 128MB cache, SATA-600 interface, Advanced Format, Shingled Magnetic Recording, 15mm z-height)

ST3000LM016 3TB (4/8 [short-stroked])

ST4000LM016 4TB (5/10)

Note: The product manual lists multiple M/Ns per capacity, and isn’t forthcoming on the differences (besides encryption); only the “016” models, which appear the most common, are listed. Drive-managed SMR use in at least the ST4000LM016 (though I wouldn’t expect “shingles or not” to be a differentiating factor between the model numbers) is highly likely, given the eerily strong performance of randomized 4K writes in CrystalDiskMark 1000MB (a consistent behaviour of SMR HDDs across manufacturers), along with talk in data recovery forums of a “media cache”.

Note 2: As with the D8Xes and M9T(U)s, these came out sometime after the Seagate buyout, and the Samsung branding on the labels is fully replaced by Seagate’s in later batches.

https://rml527.blogspot.com/2010/09/hdd-platter-database-samsung-25.html

So while as a stretch it’s possible an 800GB CMR platter existed, since it’s ~17% more data than 667GB, it’s extremely unlikely a ~35% increase to 1TB CMR could have been achieved.

What may be the answer is from this 2016 review:

All the new BarraCuda 2.5” HDDs feature 128 MB of DRAM cache as well as multi-tier caching (MTC) technology, which is designed to hide peculiarities of SMR. Hard drives featuring shingled recording write new magnetic tracks that overlap part of the previously written tracks. This may slow down the writing process since the architecture requires HDDs to rewrite adjacent tracks after any writing operation. To “conceal” such peculiarities, Seagate does a number of tricks. Firstly, it organizes SMR tracks into bands in a bid to limit the amount of overwriting. Secondly, the MTC technology uses several bands of PMR tracks on the platters, around 1 GB of NAND flash cache as well as DRAM cache. When workloads generate relatively small amount of writes, the HDD writes data to NAND and/or to the PMR tracks at a predictable data rate. Then, during light workloads or idle time, the HDD transfers written data from the caches to SMR tracks, as described by Mark Re (CTO of Seagate) earlier this year.

https://www.anandtech.com/show/10757/seagate-introduces-barracuda-25-mobile-hard-drives-with-up-to-5-tb-capacity