missing tag - turn:lanes:forward without lanes - although lanes:forward and lanes:backward are correct

[Polarbear-j]

How to reproduce:

create New Layer
draw street, tag highway and name
tag lanes:forward=1 and lanes:backward=2

try upload: validator ok

add turn:lanes:forward=left|through

try upload: Validator: "missing tag - turn:lanes:forward without lanes (1)"
===
Thus the validator requires the sum of lanes:forward + lanes:backward to be added in lanes, which is redundant and error-prone.
In particular it requires the sum only in the presence of other *:lanes tags, which is inconsequent.

Might be a side effect of #19609 ?
===
Might be unrelated but in the startup messages I found:
2020-11-03 20:39:15.377 INFO: Could not load tool definition turnlanes-tagging
===
from Status:

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2020-11-03 00:09:37 +0100 (Tue, 03 Nov 2020)
Build-Date:2020-11-03 02:30:51
Revision:17292
Relative:URL: ^/trunk

Identification: JOSM/1.5 (17292 en_GB) Mac OS X 10.14.6
OS Build number: Mac OS X 10.14.6 (18G6032)
Memory Usage: 1559 MB / 3641 MB (1372 MB allocated, but free)
Java version: 1.8.0_251-b08, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM

Plugins:
[...]
+ turnlanes-tagging (288)
+ turnrestrictions (35583)
[...]
validator.bounds=1177,534,743,587
validator.geometry=x=759,y=-772,width=1161,height=772
validator.lastHeight=76
validator.layer=false
validator.org.openstreetmap.josm.data.validation.tests.MapCSSTagChecker.entries=[{title=Addresses, active=true, url=resource://data/validator/addresses.mapcss},

{title=Tag combinations, active=true, url=resource://data/validator/combinations.mapcss},
{title=Deprecated features, active=true, url=resource://data/validator/deprecated.mapcss},
{title=Geometry, active=true, url=resource://data/validator/geometry.mapcss},
{title=Highways, active=true, url=resource://data/validator/highway.mapcss},
{title=Multiple values, active=true, url=resource://data/validator/multiple.mapcss},
{title=Numeric values, active=true, url=resource://data/validator/numeric.mapcss},
{title=Religion, active=true, url=resource://data/validator/religion.mapcss},
{title=Relations, active=true, url=resource://data/validator/relation.mapcss},
{title=Unnecessary tags, active=true, url=resource://data/validator/unnecessary.mapcss},
{title=Wikipedia, active=true, url=resource://data/validator/wikipedia.mapcss},
{active=true, title=Territories, url=resource://data/validator/territories.mapcss}

]
validator.other=true
validator.skip=[]
validator.skipBeforeUpload=[]
validator.visible=true