that is my understanding of this attempt at selling more booster packs and raising odds of people buying packs.I'm assuming the shocklands aren't in the set aka can't be your pack rare, they're just an extra gimmick prize you can get in place of your guildgate?
according to a tweet seds sent out yesterday, the distribution is 1/2 as likely to open a shockland compared to a non-DM booster, so your odds are actually pretty good given that a shockland is in your land slot.