I reproduced this by creating an inconsistent pg and then causing it to split.
pool of size 2 with 1 pg and I created an inconsistency in one object (it had 2 scrub errors, size and data_digest_mismatch)
After pg_num/pgp_num to 8, there was only 1 resulting pg on a single replica with num_scrub_errors and the value was 1.
PG_STAT OBJECTS MISSING_ON_PRIMARY DEGRADED MISPLACED UNFOUND BYTES LOG DISK_LOG STATE STATE_STAMP VERSION REPORTED UP UP_PRIMARY ACTING ACTING_PRIMARY LAST_SCRUB SCRUB_STAMP LAST_DEEP_SCRUB DEEP_SCRUB_STAMP SNAPTRIMQ_LEN
1.7 12 0 0 0 0 20048 101 101 active+clean 2018-03-21 19:46:17.366706 11'101 20:169 [1,2] 1 [1,2] 1 11'101 2018-03-21 19:43:22.172793 11'101 2018-03-21 19:43:22.172793 0
1.6 12 0 0 0 0 20048 101 101 active+clean 2018-03-21 19:46:15.176818 11'101 19:146 [1,0] 1 [1,0] 1 11'101 2018-03-21 19:43:22.172793 11'101 2018-03-21 19:43:22.172793 0
1.5 13 0 0 0 0 20048 101 101 active+clean 2018-03-21 19:46:18.414012 11'101 20:54 [2,0] 2 [2,0] 2 11'101 2018-03-21 19:43:22.172793 11'101 2018-03-21 19:43:22.172793 0
1.4 13 0 0 0 0 20049 101 101 active+clean 2018-03-21 19:46:15.181264 11'101 19:146 [1,0] 1 [1,0] 1 11'101 2018-03-21 19:43:22.172793 11'101 2018-03-21 19:43:22.172793 0
1.3 13 0 0 0 0 20049 101 101 active+clean 2018-03-21 19:46:18.724337 11'101 20:173 [1,2] 1 [1,2] 1 11'101 2018-03-21 19:43:22.172793 11'101 2018-03-21 19:43:22.172793 0
1.2 13 0 0 0 0 20049 101 101 active+clean 2018-03-21 19:46:16.187580 11'101 20:136 [0,1] 0 [0,1] 0 11'101 2018-03-21 19:43:22.172793 11'101 2018-03-21 19:43:22.172793 0
1.1 13 0 0 0 0 20049 101 101 active+clean 2018-03-21 19:46:19.378158 11'101 20:30 [2,0] 2 [2,0] 2 11'101 2018-03-21 19:43:22.172793 11'101 2018-03-21 19:43:22.172793 0
1.0 12 0 0 0 0 20048 101 101 active+clean 2018-03-21 19:46:15.174846 11'101 19:147 [1,0] 1 [1,0] 1 11'101 2018-03-21 19:43:22.172793 11'101 2018-03-21 19:43:22.172793 0
Interestingly, all the primaries have num_scrub_errors == 0, but a single post-split pg replica has a non-zero value.
1.0
"num_scrub_errors": 0,
"num_scrub_errors": 0,
1.1
"num_scrub_errors": 0,
"num_scrub_errors": 0,
1.2
"num_scrub_errors": 0,
"num_scrub_errors": 1,
1.3
"num_scrub_errors": 0,
"num_scrub_errors": 0,
1.4
"num_scrub_errors": 0,
"num_scrub_errors": 0,
1.5
"num_scrub_errors": 0,
"num_scrub_errors": 0,
1.6
"num_scrub_errors": 0,
"num_scrub_errors": 0,
1.7
"num_scrub_errors": 0,
"num_scrub_errors": 0,