why does -i paremeter not working while pipe?

[DKblue]

why does -i paremeter not working while pipe?
there should be  exist something like MASK:?l?l 1/5 or 2/5 ,but now there isn't
at first glance I think maybe a6 mode, then I tried another a6 attack and -i works fine.
So how can I make -i parameter working in pipe mode?
Atom suggest pipe many times and pipe really run fast,seldom drop speed too much.
Can anyone help? What's wrong in the code as follows with -i parameter? 

c:\hc>hashcat64 -a6 zm.txt ?l?l?l?l?l -i --stdout | hashcat64 -m 2500 -a0 --nonce-error-corrections=0 -w 3 -d 1,2 final26c4.hccapx
hashcat (v4.0.1) starting...
OpenCL Platform #1: NVIDIA Corporation
======================================
* Device #1: GeForce GTX 1060 6GB, 1536/6144 MB allocatable, 10MCU
* Device #2: GeForce GTX 1060 6GB, 1536/6144 MB allocatable, 10MCU
OpenCL Platform #2: Advanced Micro Devices, Inc.
================================================
* Device #3: Spectre, skipped.
* Device #4: AMD A10-7700K Radeon R7, 10 Compute Cores 4C+6G, skipped.
Hashes: 3 digests; 3 unique digests, 1 unique salts
Bitmaps: 16 bits, 65536 entries, 0x0000ffff mask, 262144 bytes, 5/13 rotates
Rules: 1
Applicable optimizers:
* Zero-Byte
* Single-Salt
* Slow-Hash-SIMD-LOOP
Password length minimum: 8
Password length maximum: 63
Watchdog: Temperature abort trigger set to 90c
Watchdog: Temperature retain trigger set to 75c
Starting attack in stdin mode...
Session..........: hashcat
Status...........: Running
Hash.Type........: WPA/WPA2
Hash.Target......: final26c4.hccapx
Time.Started.....: Sat Dec 02 20:37:19 2017 (9 secs)
Time.Estimated...: Sat Dec 02 20:37:28 2017 (0 secs)
Guess.Base.......: Pipe
Speed.Dev.#1.....:   174.0 kH/s (50.67ms)
Speed.Dev.#2.....:   170.6 kH/s (50.96ms)
Speed.Dev.#*.....:   345.0 kH/s
Recovered........: 0/3 (0.00%) Digests, 0/1 (0.00%) Salts
Progress.........: 5059830
Rejected.........: 2110710
Restore.Point....: 0
Candidates.#1....: lovewiee -> zhongeldr
Candidates.#2....: zhongwiee -> gunkaimnss
HWMon.Dev.#1.....: Temp: 56c Fan: 33% Util: 93% Core:1885MHz Mem:3802MHz Bus:16
HWMon.Dev.#2.....: Temp: 61c Fan: 52% Util: 78% Core:1873MHz Mem:3802MHz Bus:4

And here I tried another a6 attack and -i works fine.
c:\hc>hashcat64 -a6 -m 2500 --nonce-error-corrections=0 -w 3 -d 1,2 --session=final26c4 final26c4.hccapx sj.txt ?l?l -i
hashcat (v4.0.1) starting...
OpenCL Platform #1: NVIDIA Corporation
======================================
* Device #1: GeForce GTX 1060 6GB, 1536/6144 MB allocatable, 10MCU
* Device #2: GeForce GTX 1060 6GB, 1536/6144 MB allocatable, 10MCU
OpenCL Platform #2: Advanced Micro Devices, Inc.
================================================
* Device #3: Spectre, skipped.
* Device #4: AMD A10-7700K Radeon R7, 10 Compute Cores 4C+6G, skipped.
Hashes: 3 digests; 3 unique digests, 1 unique salts
Bitmaps: 16 bits, 65536 entries, 0x0000ffff mask, 262144 bytes, 5/13 rotates
Applicable optimizers:
* Zero-Byte
* Single-Salt
* Slow-Hash-SIMD-LOOP
Password length minimum: 8
Password length maximum: 63
Watchdog: Temperature abort trigger set to 90c
Watchdog: Temperature retain trigger set to 75c
Dictionary cache built:
* Filename..: sj.txt
* Passwords.: 6120000
* Bytes.....: 79560000
* Keyspace..: 159120000
* Runtime...: 1 sec
[s]tatus [p]ause [r]esume [b]ypass [c]heckpoint [q]uit =>
Session..........: final26c4
Status...........: Running
Hash.Type........: WPA/WPA2
Hash.Target......: final26c4.hccapx
Time.Started.....: Sat Dec 02 20:51:45 2017 (1 sec)
Time.Estimated...: Sat Dec 02 20:58:40 2017 (6 mins, 54 secs)
Guess.Base.......: File (sj.txt), Left Side
Guess.Mod........: Mask (?l) [1], Right Side
Guess.Queue.Base.: 1/1 (100.00%)
Guess.Queue.Mod..: 1/2 (50.00%)