I believe this is incorrect. FIFA refer to official and non-official competition. They specify official competition as follows:
The phrase “official competition” is defined in the FIFA Statutes as “a competition for representative teams organised by FIFA or any confederation”.
These competitions are World Cup and confederation competitions organised by the confederations (e.g, UEFA championship, Asian Cup, Nations Cups, etc).
FIFA does not define what non-official competition is, nor do they refer to or define friendlies. All games that aren't official competition are non-official competition, so non-official games include friendlies. The word "competition" in non-official competition does not mean the game has to be part of a game or series where the winner wins something, it just means that it is an organised official game (i.e., a competition) between two Member Associations (countries) under the laws of football, and not, for example, a training session, a training game, or a game against a club team.
In addition, FIFA Article 9 Paragraph 5 covers changing back to a player's original association and it reads as follows:
A player that was: a) granted a change of association; and b) was not fielded in a match in any (official or unofficial) competition in any kind of football by the new association, may request a change of association back to his former association provided he continues to hold the nationality of such association.
FIFA also include commentary on these paragraphs, and the commentary on Art 9 Para 5 is a s follows:
Article 9 paragraph 5
106. Article 9 paragraph 5 introduces a limited regulatory exception to the restriction of being granted a change of association once only. A player who receives a favourable change of association decision but is subsequently never fielded by their new MA faces an excessive hardship.
107. A player will be permitted to reverse a change of association decision where they:
107.1 were previously granted a change of association by the PSC; and
107.2 were never fielded in a match (in an official or non-official competition) by the new MA in any kind of football; and
107.3 continues to hold the nationality of their former MA.
108. A player is “fielded” in a match where they have physically played in the match, even for a matter of seconds, whether as a starter, or as a substitute for another player.
109. The phrase “official competition” is defined in the FIFA Statutes as “a competition for representative teams organised by FIFA or any confederation”.
110. “Kind of football” refers to association football, futsal, or beach soccer.
111. There is no waiting period to request the reversal of a change of association decision.
112. The word “continues” requires the player to have held the nationality of their former MA for the whole period while their “sporting nationality” was linked to their new MA. In general, if a player has abandoned the nationality of their former MA during this period, the “genuine link” between the player and their former MA is considered to have been lost.
113. The reversal of a change-of-association decision is only permitted once, to prevent abuse and protect the sporting integrity of international competition.
So this means that if Segacic plays any minutes, senior or underage, football or beach soccer or futsal, in official competition or non-official competition, i.e., friendlies, for Croatia then he is ineligible to request a switch back to Australia.
Here is a link to the complete document I am referring to: