Confusing behavior when attempting to use the HOSTALIASES environment variable

Question

See here, or man gethostbyname.

It seems to work as expected when run on a simple C program that calls gethostbyname, which I had ChatGPT write, and which includes:

    hints.ai_family = AF_UNSPEC; // AF_INET or AF_INET6 to force version
    hints.ai_socktype = SOCK_STREAM;

    status = getaddrinfo(argv[1], NULL, &hints, &res)

It seems to work as expected:

$ cat h
my_alias google.com
$ HOSTALIASES=./h          ./test_hostaliases my_alias
IP addresses for my_alias:

  IPv4: 172.253.63.139
  IPv4: 172.253.63.102
  …
$ sudo HOSTALIASES=./h   ltrace -e getaddrinfo      ./test_hostaliases my_alias
test_hostaliases->getaddrinfo("my_alias", nil, 0x7ffe8a4224b0, 0x7ffe8a4224a8)        = 0
IP addresses for my_alias:

  IPv4: 172.253.63.101
  IPv4: 172.253.63.100
  …

….but ping does not work:

$ HOSTALIASES=./h ping my_alias
ping: my_alias: Name or service not known

…but trying to debug with ltrace I realized it does work as root:

$ sudo HOSTALIASES=./h   ltrace -e getaddrinfo      ping my_alias
ping->getaddrinfo("my_alias", nil, 0x7fff7e3baba0, 0x7fff7e3bab88)                    = 0
PING google.com (142.251.111.101) 56(84) bytes of data.
64 bytes from bk-in-f101.1e100.net (142.251.111.101): icmp_seq=1 ttl=60 time=8.86 ms
$ sudo HOSTALIASES=./h       ping my_alias
PING google.com (172.253.62.100) 56(84) bytes of data.
64 bytes from bc-in-f100.1e100.net (172.253.62.100): icmp_seq=1 ttl=111 time=9.09 ms
…

What is going on here?