Whoever told you that or is an huge whale or somebody that played in 1.0 or 2.0 and that has no idea aboit how the game works now.

If you own level 10 refinement with, lets say, an 83% control (yes, it's gold even 83%...) you get 660*1.83 = 1208 control. If you, instead, were not greedy and you stopped with a purple at, lets say, 75%,you got 660*1.75 = 1155 control. Are 53 control points of difference, means you just get a 0.53% more chance to control the enemy or to not let you be controlled, the same applies to the other 3 substats. If you honestly think is worth to spend even 200+ purification protection runes to get 2 of them after you got initiative gold and 4 high purples then feel free to do it. Your enemies, in the meanwhile, will spend those 3800+ coupons in other features, like myoboku cultivation/trial/banace assist links or treasure tools or other features that give them way more than those 50/100 more substats. Even a page 13 tile in myoboku feature, that costs 182 items, give more in game effect than the difference between a decent purple and a gold.

So, if you get them for free fine, but if you have to spend even 1 single coupon on them no way.

So you don't buy bells, cave keys, myoboku gifts and advanced threads. Same thing.