The promotion is narrative, the attributes are mechanical; there exist no rules indicating how or if the two are linked outside the character Recruitment process.
My take has been that a Guardmouse (or any other rank) must show (at minimum) rating 2 in each skill which would be granted to a Patrol Guard/Leader (or other promotion, respectively) before being considered for promotion; they must also have a recommendation from one or more of that higher rank, and have a commendation from a Guard Captain or the Matriarch. But, once gaining the promotion, they have no tangible change in Traits, Skills, or Wises. As per rules, they only have an alteration to Resources and Circles.
In the case of Tendwerpaw, they similarly have no change in Traits, Skills, or Wises while gaining the benefit for Resources and Circles, and they must also have a recommendation from their Mentor or a similarly near-n-dear higher-ranked mouse who can vouch for the lessons learned as a Tenderpaw. They do not have to gain a commendation from any higher-ups to merit the promotion from Tenderpaw to Guardmouse. In that sense, earning the Guardmouse rank rest upon behaving well as a Tenderpaw while also serving as a dead-end rank for those without ambition, purpose, drive, or motivation.
For the Patrol Guard/Leader, it is best they take up a new Mentor under a Guard Captain or the Matriarch in order to properly prepare for continued promotions upward. That is, in case their first Mentor is not among those highest ranks.
Honestly, I haven’t run a promotion in-game for quite a long time, and I’ve only ever run promotions for Tenderpaw to Guardmouse. So, take from my comments only what you wish; little of what I say has much experience behind it in this topic.