I don't think that's right at all. It might be true in the USA, but that's only like 3 providers, isn't it?
I'm in the UK and I don't have IPv6 on my mobile or at home. I travel to ROI often and my phone has never picked up on IPv6 address. I was in Italy a couple weeks ago and I never got an IPv6 address. I know I checked because a friend of mine keeps telling me bullshit like this about how real IPv6 is, and I've never had an IPv6 address.
I was in Spain at the beginning of the year and didn't get one; and Germany late last year: No IPv6.
Mobile networks use a lot of IPv6 internally, but that is invisible to the customer. Your IPv4 or v6 traffic in tunnelled inside IPv6 between nodes of the cellular network. That may be the cause of some confusion.
But are you roaming in those places? For reasons I don't understand fully but are presumably billing related your IP traffic gets tunnelled back to your home ISP when roaming, or at least, it used to.
In Germany, only Deutsche Telekom (and resellers such as Congstar) supports IPv6 on mobile (for both prepaid and postpaid). And it works great, even when tethering.
Since you're from the UK, I suppose you are a Vodafone customer and therefore roaming in the Vodafone network in Germany (which does not support IPv6 yet).
On some networks/devices you might have to enable IPv6 explicitly, by setting the APN to IPv4/IPv6.
In Singapore, Singtel seems to be the only provider that supports IPv6. Unfortunately only for postpaid plans.
Is that in the US? In my Eastern European country, IPv6 has not become directly available to mobile customers. One of our major ISPs began offering IPv6 addresses for fiber customers over half a decade ago; all the customer needs to do is set up PPPoE on the router and the connection automatically gets both IPv4 and a couple of IPv6 addresses. But if you add mobile internet to your contract with that ISP, that mobile connection still only provides an IPv4 address that I assume is NATed to hell. The same is true of internet connections through a large pan-European mobile provider here.
I don't think that Canadian ISPs are in on this. In particular, almost all Canadian mobile customers are on Bell, TELUS, and Rogers. I'm on TELUS right now and I fail test-IPv6.com. Telus and Bell actually share much of their mobile network so I'm not sure Bell would fare better. And I was on Rogers as recently as 6 months ago and they didn't have IPv6 either. And my home ISP, a small fibre ISP, doesn't have IPv6.
I'm on Fido/Rogers in Quebec/Ontario, and they have had IPv6 enabled for 1-2 years. Make sure that your APN settings enable IPv6 (in Android, there's an option for that).
Mobile is the main reason why Canada is >15% adoption on google-stats [1]. On DSL/cable, Rogers and Cogeco provide IPv6, as do smaller re-sellers such as Teksavvy on DSL, but otherwise big players such as Bell and Videotron have been dragging their feet and giving lame excuses.
I tried a few months ago and can enable IPv6 on my LG V20 (on Telus LTE) and it does indeed pick up an IPv6 address but test-ipv6.com complains of MTU problems.
Sites did load over v6 but it was slow compared to v4.
LTE or DSL? I'm on LTE in Vancouver and it fails (and has consistently in the last 6 months).
Are you in Calgary? Telus always rolls out experiments in Calgary first. For example, until recently their only deployed GPON networks have been in Calgary subdivisions.
