I guess what Bolt is trying to say is that since Scizor only has Pursuit and U-Turn to work with, it really doesn't gain much with sweeping potential. SD gives so much sweeping power, but you're using it only for landing one big hit, then the boosts are lost. Since the Scizor has more of a utility niche with that moveset, some people might think another support move would be more beneficial.
As for Suicune, Substitute isn't the best idea, as it drains Suicune of spare HP, and it needs the HP to maintain its bulkiness. That's why most Suicune sets use Rest, to avoid status. SleepTalk or Crocune sets work fairly well. You could use Sub if you want, but like other people think, it may not be the best option. And it's not like a sub will completely protect you from a switch-in counter. If it's a true counter, you'll have to retreat Suicune sooner or later.
As for Suicune, Substitute isn't the best idea, as it drains Suicune of spare HP, and it needs the HP to maintain its bulkiness. That's why most Suicune sets use Rest, to avoid status. SleepTalk or Crocune sets work fairly well. You could use Sub if you want, but like other people think, it may not be the best option. And it's not like a sub will completely protect you from a switch-in counter. If it's a true counter, you'll have to retreat Suicune sooner or later.