Circle Arc tool creates unconnected nodes

[Hb---]

What steps will reproduce the problem?

1. Draw a way with some nodes.
2. Select non-adjacent nodes like 2, 4 and 5 and the way.
3. Invoke Circle Arc tool (Shift+C)

What is the expected result?

A circle arc formed between the segments 2, 3 and 4.

What happens instead?

Some free nodes gets created (under node 3 in the screenshot).

The current behavior does not fit to the "Method 3" from the help and not to the authors comments in the ​class header.

URL:https://josm.openstreetmap.de/svn/trunk
Repository:UUID: 0c6e7542-c601-0410-84e7-c038aed88b3b
Last:Changed Date: 2020-02-29 00:28:12 +0100 (Sat, 29 Feb 2020)
Build-Date:2020-02-29 02:31:03
Revision:15958
Relative:URL: ^/trunk

Identification: JOSM/1.5 (15958 en) Windows 7 64-Bit
OS Build number: Windows 7 Professional (7601)
Memory Usage: 1450 MB / 3604 MB (1269 MB allocated, but free)
Java version: 1.8.0_212-b03, AdoptOpenJDK, OpenJDK 64-Bit Server VM
Screen: \Display0 1280x1024
Maximum Screen Size: 1280x1024
VM arguments: [-Djosm.home=testrun]
Program arguments: [--language=en]
Dataset consistency test: No problems found

Plugins:
+ utilsplugin2 (35334)

Last errors/warnings:
- W: Failed to parse external taginfo data at https://josm.openstreetmap.de/remote/geofabrik-index-v1-nogeom.json: Invalid token=EOF at (line no=6119, column no=2252, offset=359085). Expected tokens are: [CURLYOPEN, SQUAREOPEN, STRING, NUMBER, TRUE, FALSE, NULL]
- E: Failed to locate image 'https://josm.openstreetmap.de/browser/trunk/images/copy.svg?format=raw'