The Bronze Scout Clockwork construct from Mordenkainen's Tome of Foes (p. 125) is a CR1 monster, but has a set of traits that seem to make it incredibly powerful, unless I'm interpreting them incorrectly.
Speed 30 ft., burrow 30 ft.
Earth Armor. The bronze scout doesn’t provoke opportunity attacks when it burrows.
Based on the basic idea that players and monsters can move and attack in any combination (as in, move 15ft, attack, move the remaining 15ft), what is stopping the Bronze Scout from burrowing 15ft up to the surface to attack a PC, then burrowing down 15ft after, which according to Earth Armor, would not trigger an Opportunity Attack?
If I'm reading this correctly, how could the PC's counter attack or stop the Scout from re-burrowing on its turn? My first thought was that the PCs could set up their reaction to attack it, but since you cannot move AND attack on a Readied Action, the PCs would have to hope that the construct would attack one of them that other allies were adjacent to.
Finally, the flavor description of the Scout (on p. 124) indicates that it can see above ground when burrowing:
A bronze scout seldom emerges from below ground; thanks to its telescoping eyestalks, it can observe enemies at close range while most of its segmented, wormlike body remains buried.
Its got an INT of 3 and a WIS of 14, so I feel that it should be able to make good attack decisions on its own, such as selecting a target to pop out and attack whom doesn't have a squad of allies standing beside it ready to counter attack.
Finally, the creature hits with a melee attack of 1d4+3 plus 1d6 lightning damage, and it has a once-per-rest area lighting attack that does 4d6, so its seems kind of lethal for a pack of 1st level characters.
Am I reading these rules incorrectly or is this monster much stronger tactically than a CR1 would suggest?