Unexpected "Overlapping ways" warning on overlapping indoor rooms

[OSMDoudou]

What steps will reproduce the problem?

Draw two overlapping (but joined) indoor=rooms areas, like [1] and [2].
[1] ​https://www.openstreetmap.org/way/94831506
[2] ​https://www.openstreetmap.org/way/94831508

What is the expected result?

Just like two buildings with merged nodes may overlap, two indoor rooms should be allowed to overlap without warning.

What happens instead?

An unexpected warning message "Overlapping ways" is raised upon save.

Please provide any additional information below. Attach a screenshot if possible.

This issue was discussed already here: [3] and [4].

[3] ​https://lists.openstreetmap.org/pipermail/tagging/2018-January/034925.html
[4] ​https://help.openstreetmap.org/questions/61383/josms-overlapping-ways-warnings-when-mapping-indoors

Relative:URL: ^/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2017-12-31 03:09:43 +0100 (Sun, 31 Dec 2017)
Revision:13265
Build-Date:2017-12-31 02:33:46
URL:http://josm.openstreetmap.de/svn/trunk

Identification: JOSM/1.5 (13265 en) Windows 10 64-Bit
OS Build number: Windows 10 Enterprise 1709 (16299)
Memory Usage: 192 MB / 1024 MB (47 MB allocated, but free)
Java version: 9.0.1+11, Oracle Corporation, Java HotSpot(TM) 64-Bit Server VM
Screen: \Display0 1600x900
Maximum Screen Size: 1600x900
Dataset consistency test: No problems found

Plugins:
+ OpeningHoursEditor (33876)
+ RoadSigns (33798)
+ alignways (33784)
+ buildings_tools (33735)
+ imagery_offset_db (33774)
+ turnlanes (33858)

Last errors/warnings:
- W: No configuration settings found.  Using hardcoded default values for all pools.

[simon04]

In 15369/josm:

fix #15815 - OverlappingWays: exclude indoor=