I encountered the problem that after I chose backend device as /dev/emcpowera3 I have seen 16+1 bcache-devices (bcache0-bcache16). It reflected from the fact that bcache saw all links (reading the bcache signatures).
The solution apears to be very simple:

vi /usr/lib/udev/rules.d/69-bcache.rules 
was:
KERNEL=="fd*|sr*", GOTO="bcache_end"
should be:
KERNEL=="fd*|sr*|sd*", GOTO="bcache_end"

How it looked before I changed udev rule:

ls -l /dev/bcache* | wc -l
17
lsblk -o NAME,MAJ:MIN,RM,SIZE,TYPE,FSTYPE,MOUNTPOINT,UUID | grep 2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J

├─sdb1                    8:17   0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
a├─sdc1                    8:33   0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─sdd1                    8:49   0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─sde1                    8:65   0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─sdf1                    8:81   0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─sdg1                    8:97   0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─sdh1                    8:113  0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─sdi1                    8:129  0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─sdn1                    8:209  0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─sdo1                    8:225  0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─sdp1                    8:241  0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─sdq1                   65:1    0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─sdr1                   65:17   0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─sdw1                   65:97   0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─sdx1                   65:113  0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─sdy1                   65:129  0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J
├─emcpowera1            120:1    0   1.9G part  LVM2_member                  2YbyAH-d3D3-0G1g-d4nO-LVrd-c59i-HWAW0J

After:

ls -l /dev/bcache* | wc -l
1