During a trail race, the terrain can magnify many of those strengths and weaknesses.
Feeling a little apprehensive about a technical section, whoosh, there goes someone with nimble feet right by you. Your strength may be climbing, in which case you’ll pass them right back on the next hill. If you then focus on your technical ability you may gain a few seconds through that techy section but in the process neglect your climbing ability, you won’t be passing anyone back when you hit the next hill.
Think about hills for a minute. For me, my uphill climbing ability is both a strength and a weakness, depending on who I’m running against and what kind of race I’m racing. In a road race with rolling hills, it’s a huge strength but getting into a pure mountain race with great climbers, it’s been a weakness. Working on my climbing ability as a weakness by including more runs with easy elevation gain, finding longer mellow climbs that I can settle into and find a good sustainable rhythm, has been a huge benefit to not only my climbing ability during races but also my overall strength for racing shorter, flat races as well. Not to neglect my strength however, I still use short hill workouts for that VO2max, power and explosiveness I need for shorter distance races.