Time limits for endurance races

Recently, I was joking that the first thing I check for in a race is the max time limit. Some marathons have time limits, such as 7 hours for Bangkok (no time limit for SCSM!) In particular, on the subject of multi-sports events, I was concerned about the time limit for the swim leg in a triathlon. So checked out the websites:

OSIM triathlon 1.5 km swim: 50 minutes (1m 40sec per 50m lap)
70.3 Aviva Ironman 1.9 km swim: 70 minutes (1m 50sec per 50m lap)

Interestingly, the limits for the bike and run legs are based on the original start time:

Bike – 90.1kms - Cut off is 5:30 after your original wave start. (4:20 assuming max swim time - 19 km/h speed)

Run - 21.1kms - Cut off at the finish is 8:30 after your original wave start. (3 hours assuming max swim and bike times - 8:30 pace)