I got a WD My Book 8 TB (WDBBGB0080HBK-EESN) and after some testing it looks like a non-SMR drive.
See CDM screenshot attached (the disk was 99.999% full, to make it "sweat", the test with 0% full is almost the same except the SEQ values being 199MB/s).
Also test with FIO as per this post suggests it is not SMR. The summary:
TEST: (groupid=0, jobs=1): err= 0: pid=4768: Tue Sep 10 22:24:49 2019
write: IOPS=7, BW=73.2MiB/s (76.8MB/s)(85.8GiB/1200024msec)
slat (usec): min=353, max=4294.0k, avg=2579.76, stdev=71064.79
clat (usec): min=2, max=9319.4k, avg=69451.95, stdev=100307.35
lat (msec): min=35, max=402895, avg=136.54, stdev=4401.42
clat percentiles (msec):
| 1.00th=[ 41], 5.00th=[ 47], 10.00th=[ 51], 20.00th=[ 57],
| 30.00th=[ 61], 40.00th=[ 64], 50.00th=[ 67], 60.00th=[ 70],
| 70.00th=[ 74], 80.00th=[ 80], 90.00th=[ 87], 95.00th=[ 93],
| 99.00th=[ 114], 99.50th=[ 188], 99.90th=[ 234], 99.95th=[ 239],
| 99.99th=[ 9329]
bw ( KiB/s): min=19922, max=183585, per=100.00%, avg=144614.45, stdev=17834.58, samples=1226
iops : min= 1, max= 17, avg=13.38, stdev= 1.78, samples=1226
lat (usec) : 4=0.02%, 20=0.02%, 50=0.05%, 100=0.01%
lat (msec) : 50=9.84%, 100=87.85%, 250=2.17%, 500=0.02%
cpu : usr=0.33%, sys=0.42%, ctx=0, majf=0, minf=0
IO depths : 1=100.0%, 2=0.0%, 4=0.0%, 8=0.0%, 16=0.0%, 32=0.0%, >=64=0.0%
submit : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
complete : 0=0.0%, 4=100.0%, 8=0.0%, 16=0.0%, 32=0.0%, 64=0.0%, >=64=0.0%
issued rwts: total=0,8788,0,0 short=0,0,0,0 dropped=0,0,0,0
latency : target=0, window=0, percentile=100.00%, depth=1
Run status group 0 (all jobs):
WRITE: bw=73.2MiB/s (76.8MB/s), 73.2MiB/s-73.2MiB/s (76.8MB/s-76.8MB/s), io=85.8GiB (92.1GB), run=1200024-1200024msec