Actually, if you understand the fundamentals of running, you'll realise that the easy runs from running can be substituted for swimming/cycling cross training. The important ones to do are: long run, intervals, threshold. Can alternate intervals and thresholds across the weeks. You'll end up running less but still able to sustain the running pace by doing swimming/cycling. With 20-30+ km, it's more than sufficient to run a HM, especially if coupled with cross training.
Yi Jun HM is fast, mostly because of Vo2max. His NS IPPT days can easily get 8.30, similar to Aaron. That's why both of them can do well without needing to run much. Aaron averages about 35-40km weeks of running throughout the year, can hit 1.20.
But ultimately, that mileage definitely not sufficient for the marathon. Yi Jun tried marathon but hit the wall, whereas Aaron did marathon but was more of a casual experience than try for times.
Got to train transitioning if not hard to do well in dual/triple athletic sports. That's the part I don't really like since I usually do training separately. Even for NS IPPT, I don't like to do push ups/sit ups then run. Prefer to do in separate time frames.
If it's a competition, people will tryhard and not overthink so much. Too much adrenaline liao, from start to end, just push through even if they feel tired.
Good advice, the korea ex military video I shared yesterday. That guy made his 3k pace become his 5k pace in 1 year of training. After hitting his 5k PB, ran the HM, with most runs being 12-13km at most. Run 1.22

Working on short distances is very important to hit the pace for long distance running.
I am going for that too, haven't thought of a race strategy for the 10k yet. Will figure out in the weeks to come when I train more.