Anycast for IPv4 and IPv6 not a same

Hi

I live in Buenos Aires, Argentina.

When use only IPv4 with my internet provider (Movistar with fiber) on my home, anycast is Brazil for 1 and 2.

When use IPv6, anycast2 is Brazil (34ms ping) and anycat1 is Miami (131 ms ping), selecting this last one by default to resolve requests.

I use anycast because use Tailscale VPN for my devices and is a only option.

Results of ping.nextdns.io:

edgeuno-bue           6 ms  (ultralow1)

  anexia-bue            6 ms  (ultralow2)

  edgeuno-bue (IPv6)    7 ms  (ultralow1)

  anexia-bue (IPv6)    16 ms  (ultralow2)

  edgeuno-scl          30 ms

  edgeuno-scl (IPv6)   31 ms

  vultr-sao (IPv6)     34 ms  (anycast2)

  zepto-sao (IPv6)     35 ms

  edgeuno-sao          35 ms

  edgeuno-sao (IPv6)   35 ms

  zepto-sao            35 ms

  vultr-sao            36 ms

  anexia-sao (IPv6)    38 ms

  edgeuno-cwb          45 ms

  edgeuno-poa (IPv6)   53 ms

  edgeuno-cwb (IPv6)   56 ms

  edgeuno-poa          58 ms

  edgeuno-rio          59 ms  (anycast1)

  anexia-sao           87 ms  (anycast2)

■ vultr-mia (IPv6)    131 ms  (anycast1)

  anexia-scl (IPv6)   156 ms

  anexia-scl          174 ms

Diag tool from Mac with IPv6 conection:

https://nextdns.io/diag/19d1e450-08a4-11f0-b8d9-cd671efdc728

I need information about two thing:

- Is possible same location for both anycasts endpoints with similar ping or selection with less ping option.

- Anycast in Buenos Aires to reduce latency.

Best!