Mails sent in IPv4 while I expect IPv6

[Mik J]

Hello,
My server has an IPv6 adress and is able to contact gmail mail server$ telnet 
2a00:1450:400c:c0a::1a 25Trying 2a00:1450:400c:c0a::1a...
Connected to 2a00:1450:400c:c0a::1a.
Escape character is '^]'.
220 mx.google.com ESMTP q7-20020a05600c46c700b003d9f3cf68d3si5203102wmo.92 - 
gsmtp

I relay using this ruleaction RELAIE relay
match from local tag DKIM_SIGNE for any action RELAIE

But when I look at my logs, the mails are sent over IPv4smtpd[30274]: 
79ebd464bef0b2e0 mta delivery evpid=d2651839f3f0795f from=<myu...@mydomain.org> 
to=<usert...@gmail.com> rcpt=<-> source="10.1.2.2" relay="142.251.5.27 
(wg-in-f27.1e100.net)" delay=1s result="Ok" stat="250 2.0.0 OK  1673402672 
g14-20020adfa48e000000b00285261d0e19si12019405wrb.385 - gsmtp"

Any idea why this would happen ?
version: OpenSMTPD 7.0.0