min skill delay not working properly

[Tome130]

https://youtu.be/Xz8ABna4-uQ

So I have a pre renewal server.
my renewal.h has renewal mechanics disabled

#define DISABLE_RENEWAL

//#define RENEWAL

//#define RENEWAL_CAST

when i set min_skill_delay_limit: 3000 (3 sec) it works properly, but when its set to 0 i still have 0.5 sec delay on skills wich should not have delay
{
    Id: 401
    Name: "CH_SOULCOLLECT"
    Description: "Zen"
    MaxLevel: 1
    Hit: "BDT_SKILL"
    SkillType: {
        Self: true
    }
    DamageType: {
        NoDamage: true
    }
    InterruptCast: true
    CastTime: 2000
    SkillData1: 600000
    CoolDown: 0
    Requirements: {
        SPCost: 20
    }
},

only info i could find was this https://www.gitmemory.com/issue/rathena/rathena/4254/514001674
is it really client side thing or am I missing something?

 

[4144]

min_skill_delay_limit minimal value is 10

smaller i think will allow exploit with skills casting