No.
Knives free (as names say) is for all players.
Wait, let me introduce you to a plugin a little bit.
Typing /knife will show up menu. Now it is not like many knife mods where you just type /knife and you pick knife you like if you have required level. This code is a little bit "advanced" (oh God, the cringe). Typing /knife displays:
1) Free Knives
2) VIP Knives
3) Admin Knives
4) Zixon Knives
5) Tron Knives
Free knives = no flags (z for normals users i guess)
VIP Knives = ADMIN_BAN (Currently, will change it as soon as i find good VIP plugin and set custom flag)
Admin Knives = ADMIN_BAN
Zixon Knives = ADMIN_BAN
Tron Knives = ADMIN_BAN (All of them will have custom flags, ADMIN_BAN is here for test).
So when you have required flag, you can access the thing you want to take. And if you wonder, any other knives (except free) require no EXP.