He suggests to start with as many as 20 reps per set so you don’t injure yourself, then drop some reps while increasing weight slowly till you’ve built good form and confidence to hit the ~5 rep range without injury.
This is not necessary and has some tradeoffs worth considering. 20 reps builds more fatigue than 2x10 which builds more fatigue than 3x7 which builds more fatigue than 4x5, if all at same load.
It’s better to break up sets into smaller chunks for skill acquisition.
It’s better to break up sets into smaller chunks for fatigue management and injury prevention.
There is no reason to ever go higher than 10 reps, and one could argue even 8 reps, for endurance folks.
Higher rep counts per set = higher metabolite accumulation and working closer to failure at higher rep counts also drives greater hypertrophy, neither of which are ideal for endurance sport athletes.
All the same skill acquisition can be gained with higher number of sets of lower reps, with the same very low loads that’d be used in a 20-rep set.
I’m 185lbs, and found that my newb’gains came fast. I started with 5 sets of 10x 135 for the first 3 sessions and made sure I wasn’t sore from bad form. Then I felt confident enough for 10x 185 for about a week before trying 10x 225.
For me it was mostly about building awareness and confidence with higher loads and nobody checking my form at first. Glad to see you intuitively implemented a better approach than the 20-rep approach. Our personal intuition is pretty smart sometimes. 
My personal experience has been very positive. I’ve replaced about 1/3rd ~4 hrs/week of running and cycling volume for weight room training but I have been getting 1-2 minute power PRs on bike and my runs are improving as well. This is a very common experience. I’d expect that there will be a progressively more delayed positive effect on progressively longer power domains, especially once you’ve exhausted all newbie gains in the weight room and transition back to a slightly higher emphasis on long-duration power.
Much of the movement economy gains, and resultant endurance performance enhancement from lifting happen with very limited lifting emphasis and happen early on alongside the newbie gains in the gym. Motor unit coordination is a beautiful thing! (result of lifting) So, while lifting big numbers is not mission critical for endurance performance, it absolutely can lay the groundwork for improved endurance sport performance, especially for a person with low training age in lifting.