Is it possible that the values are exchanged compared to the version of LEDE 17.01.6?
OpenWrt 18.06.1 - Archer C2600
# iw dev wlan1-1 station get C4:43:8F:C2:77:58
Station c4:43:8f:c2:77:58 (on wlan1-1)
inactive time: 34850 ms
rx bytes: 381136
rx packets: 4034
tx bytes: 32206894
tx packets: 21819
tx retries: 0
tx failed: 0
rx drop misc: 119
signal: -43 [-49, -46, -53, -53] dBm
signal avg: -43 [-51, -45, -53, -52] dBm
tx bitrate: 1.0 MBit/s
rx bitrate: 72.2 MBit/s MCS 7 short GI
authorized: yes
authenticated: yes
associated: yes
preamble: short
WMM/WME: yes
MFP: no
TDLS peer: no
DTIM period: 2
beacon interval:100
short preamble: yes
short slot time:yes
connected time: 3509 seconds
LEDE 17.01.06 - HG556a
# iw dev wlan1-1 station get C4:43:8F:C2:77:58
Station c4:43:8f:c2:77:58 (on wlan1-1)
inactive time: 3364 ms
rx bytes: 75049
rx packets: 624
tx bytes: 95818
tx packets: 263
tx retries: 23
tx failed: 24
rx drop misc: 0
signal: -38 [-39, -47] dBm
signal avg: -39 [-40, -48] dBm
tx bitrate: 65.0 MBit/s MCS 7
rx bitrate: 1.0 MBit/s
expected throughput: 31.218Mbps
authorized: yes
authenticated: yes
associated: yes
preamble: short
WMM/WME: yes
MFP: no
TDLS peer: no
DTIM period: 2
beacon interval:100
short preamble: yes
short slot time:yes
connected time: 104 seconds
Also, I see that the "expected throughput" value has been removed.