Well if it's stated that a Pillar creates a Golden Hourglass then it would seem common sense to assume a Tower would create an Electrum Hourglass.
But maaaaaybe that does need changing. Based on the wording as is I could assume that:
1) pillars refers to Pillars and not Towers or Pendulums, meaning only the former could be targeted.
2) pillars refers to unupped and upgraded Pillars, which would then mean, based on the text, that both Pillars and Towers create a Golden Hourglass.
I think it would be simpler just to say that it turns into an Hourglass and let common sense do the rest, to avoid confusion.