disguised packets, blocklist behavior

[Sting0r]

Hey guys, does anyone can explain why the packets have to be changed when casting spells while disguised?
For example in clif_skill_poseffect
 

void clif_skill_poseffect( block_list& bl, uint16 skill_id, uint16 skill_lv, uint16 x, uint16 y, t_tick tick ){
	PACKET_ZC_NOTIFY_GROUNDSKILL packet{};

	packet.PacketType = HEADER_ZC_NOTIFY_GROUNDSKILL;
	packet.SKID = skill_id;
	packet.AID = bl.id;
	packet.level = skill_lv;
	packet.xPos = x;
	packet.yPos = y;
	packet.startTime = client_tick( tick );

	if (disguised(&bl)) {
		clif_send( &packet, sizeof( packet ), &bl, AREA_WOS );
		
		packet.AID = disguised_bl_id( bl.id );
		clif_send( &packet, sizeof( packet ), &bl, SELF );
	} else {
		clif_send( &packet, sizeof( packet ), &bl, AREA );
	}
}

why the packet.AID is changed to basically -bl.id ? for the disguised player, how does that effect the client? and why when i tried to just yet the code, i changed nothing ? (just keeping clif_send( &packet, sizeof( packet ), &bl, AREA );)

[StiveRO]

There has been a complete structural change to the blocklist system, which has impacted the entire server—even though such a change was unnecessary. This has caused issues for many scripts, including those developed from the beginning. Actions like this are generally avoided in professional practice.

For example, platforms like Windows, Android, Apple, Linux, and others do not make changes to core structures lightly. Doing so would immediately cause problems for all developers relying on those structures. Even fundamental server commands have been affected, and there may still be other issues that have yet to be discovered.

[Sting0r]

It was the case also prior what you describe, i just want to know why not disguised the bl.id (wich is accountid) for example 2000001, is turned to -2000001 when disguised, what does the client make of it ^^