The website listed as latest version is Archer AX6000(US)_V1_210511. Totally different?
The box has IMDA sticker and is bought from Amazon SG (Sold and shipped by Amazon Asia-Pacific). Is local set.
unit with IMDA stickers is at least an assurance it is local set, for local conditions, and should have pre-installed sg-specific firmware.
it's been a long time since i updated my old TP-Link routers, but from what i remember, for my routers, sg used the same fw as usa.
the sg website would list all versions, but would have a note saying which country it is for. thus, the latest may have a note that said, for example, "for XXX country, to address issues of <ISP in XXX country>
having said that, I've flashed latest versions but for other countries, by mistake. didn't see any performance difference. but YMMV.
edit: just visited their site. funny how the "support" link is now hidden in the overflow menu.
did you check what hardware version your router is?
Ver 2.6 has only 1 firmware release listed
ver 2 and 1 have 2 or more.
the version you listed (AX6000(US)_V1_210511) is the latest for hardware ver 1. which matched your router.
looking at the release dates, the actual version is dated 19 jul 2021, the website version is dated 02 Jul 2021.
given that your actual version seems to be slightly more recent than the website, you could live with it.
or, if you prefer to go by the website, you could take a
not-recommended chance to flash the website version. since tp-link usually prevents flashing older firmware (via normal documented method), it will probably block this.
Disclaimer: this is a
not-recommended option. if you decide to go this route, all responsibility is yours