Question: Major Forex Centers Around the World?

[RFSmithers]

Here's a question about the meaning of "major forex centers around the world". Recently, I saw a list which listed the "major forex centers around the world" and the times they are open. Here is the list:

Wellington, New Zealand; Sydney, Australia; Tokyo, Japan; Hong Kong, China; Singapore; India; Dubai; Frankfurt, Germany; Zurich, Switzerland; Paris, France; London, UK; Johannesburg, South Africa; New York, USA; Toronto, Canada; Chicago, USA.

I know that the major trading sessions are three (Asia/Tokyo, Europe/London, Americas/New York) with the traditional forex centers considered to be in Tokyo, London and New York; and the forex market is made up of the decentralized interbank market.  So when the list shows the locations above as the "major forex centers around the world" what exactly is it referring too?

1. Major banks (participating in the interbank system) in those cities are big participants in the forex markets
2. Retail forex traders in those cities/areas are big participants in the forex markets
3. Those cities are hubs for firms/institutions which participate/trade in the forex markets
4. Those cities are hubs in terms of infrastructure for the forex markets (interbank system)
5. Location just needs to be a major global financial hub, which in turn will generate forex transactions from the cities location
6. All of the above

What exactly is meant by "major forex centers around the world" and how is a location considered a "major forex center around the world" (what criteria does a location have to pass to be considered a "major forex center around the world")?

Edited June 14, 2021 by RFSmithers