People on the e-Sangha web forum have said that Ngak’chang Rinpoche frequently changes his story about who his teachers were. (Recently someone said “every few months.”) They imply he has had to do that each time skeptics disproved his earlier claims to have been a student of someone.
This has been said so often that some people accept it without question, as an urban legend.
However, it is factually false. You can check it objectively for yourself.
Archive.org is a service that maintains old versions of web sites. You can access its archive of the Aro web site at http://web.archive.org/web/*/http://aroter.org/. The earliest version it has is November 11th, 1998.
Compare that with the current version. They are identical.
The 1998 version of the web site also has a textual biography which discusses his teachers. It does not describe any as either “root” or not. It includes the same list, with two exceptions. It mentions Könchog Rinpoche, and does not include Khamtrül Yeshé Dorje Rinpoche. The current version of his biography includes Könchog Rinpoche as an important non-root teacher. It also includes Khamtrül Yeshé Dorje Rinpoche. The 1998 version (which was written much earlier) omitted him due to the breakdown in their relationship.