Making it Jr. VIP only isn't a safety measure against Pinterest employees finding methods -- it's a safety measure against immediate and widespread saturation of any method that's shared. Not all methods rely on loopholes or easily traced footprints that Pinterest employees can mobilize against -- simply put, sharing something in front of a Pinterest employee doesn't mean the method is immediately dead, or untwistable, or anything like that.
But sharing it in front of the entire internet, where the only barrier to entry is < $100 for bots / accounts or $0 if you do it manually -- that will kill a method in no time. Flooding the site with poorly thought out spam will certainly make something drastic happen. But Jr. VIPs twisting a method and actually trying to seamlessly market within the platform is something different. Something that a Pinterest employee can't protect against just by knowing what they're up against.