Unusual Tagging Issue - aws_vpn_connection

I have come across an unusual issue when using terraform v0.12.20 and tags in aws_vpn_connection - this is not an error, more an emission.

resource aws_vpn_connection is configured for a transit_gateway_id connection. The VPN connection is successfully created and tagged.

The resource aws_vpn_connection is also managing the attachment of the VPN connection to the Transit Gateway “under the hood”. This also completes without error.

The issue I have is that the vpn connection Transit Gateway Attachment cannot be tagged.

It seam that resource aws_vpn_connection creates 2 resources but only tags 1.

site-to-site VPN Connection is tagged
VPN Transit Gateway attachment cannot be tagged

Here is my code:

resource "aws_vpn_connection" "vpn_connections" {
  for_each              = var.vpn_config
  customer_gateway_id   = aws_customer_gateway.customer_gateways[each.key].id
  transit_gateway_id    = aws_ec2_transit_gateway.tgw.id
  type                  = aws_customer_gateway.customer_gateways[each.key].type
  tunnel1_preshared_key = aws_ssm_parameter.vpn_preshared_keys[each.key].value
  tunnel2_preshared_key = aws_ssm_parameter.vpn_preshared_keys[each.key].value

  tags = merge(var.default_tags, local.vpn_service_tag, {
    "Name" : "${each.value["name"]}-vpn"