[TheXeon]

Makes sense. Just did a bit of checking with below:

Spoiler

#pragma newdecls required
#pragma semicolon 1

#include <sourcemod>

public Plugin myinfo = {
	name = "[TF2] ClientAuthTestStuff",
	author = "TheXeon",
	description = "Small plugin to test spec stuff.",
	version = "0.0.1",
	url = "https://www.neogenesisnetwork.net/"
}

public void OnClientConnected(int client)
{
	CreateTimer(10.0, AuthCheckTimer, GetClientUserId(client));
}

public Action AuthCheckTimer(Handle timer, int userid)
{
	int client = GetClientOfUserId(userid);
	if (!IsClientInGame(client))
	{
		PrintToServer("An extraneous check: client is not in-game.");
		return;
	}	
	char auth[24];
	if (!GetClientAuthId(client, AuthId_Steam2, auth, sizeof(auth)))
	{
		PrintToServer("[1] GetClientAuthId(client, AuthId_Steam2, auth, sizeof(auth)) is false.");
		if (!IsClientAuthorized(client))
		{
			PrintToServer("[2] IsClientAuthorized(client) is false."); // Yea, this is always true
		}
	}
	PrintToServer("Make sure we reached [2] here, otherwise inconsistent.");
	if (StrContains("STEAM_ID_STOP_IGNORING_RETVALS", auth, false) != -1)
	{
		PrintToServer("[3] String contains STEAM_ID_STOP_IGNORING_RETVALS");
	}
	PrintToServer("If we reached [3], but not [1] and [2], then GetClientAuth can return true even when RETVALS was obtained.");
}

and it seemed to reach 3 consecutively. Do you know if downned Steam servers might trip up GetClientAuthId? If it does, then would kicking also false-positive?