That 70% training is fine, but if you're a starting weighlifter or having any intentions to go on gym, i wouldn't exactly stop the set at 7 if you could do 10. You can easily leave 1 rep hanging there, but 1 wouldn't leave 3. Those starting strength programs are just fine for any newcomers, just because adding weight is probably the best way to get the beginner gains. When your body starts to slowly refuse getting stronger with those basic straight sets of 8-12 reps, then it's time add the volume, add the frequency and make different programs in order to keep improving, to give new stimulus for your muscles because adding more weight doesn't work anymore. It could be that your first 2 years are all about eating properly and then adding more weight weekly, should never go ahead and copy some pro bodybuilder program with 25 sets for back, 25 sets for arms etc and start from that, because you can easily get gains by doing less. Those pro programs are for those guys who have trained multiple years, even +10 and their strenght levels are already there, their recovery capacity is higher and they don't really get anything from straight sets anymore etc. You could have a guy who has never been at gym + never really been involved on any physical activity and he goes there first time, he can do 10 squats with his bodyweight and he will definitely get enough stimulus for his muscles to realize that something's wrong, we need to adapt and they're doing it by growing. Other scenario is that you copied that program from the internet, went ahead and did all those sets, reps etc and you still got that stimulus, but it doesn't make them grow any faster so it's all waste to do more, even less would have been enough.
Another thing is that central nervous system which is something that doesn't get sore, but there's a limit for it as well. Any badly slept night, any lifting, over training, working, stress or any activity in general affects on it. Basically there's a Sympathetic nervous system(SNS) which is like a fight/flight mode and then the opposite for that is parasymphatic nervous system(PNS) which is like a complete opposite to that, like a rest n digest and the more you're in that SNS mode aka the fight/flight mode, the higher is the risk of going beyond of what you're capable of. So for example you're father of 3 and you're doing physical work and doing night shifts while lacking sleep but you would still like to hit the gym for 5x a week and do heavy lifting even it's just 70%, there's higher risk to have somekind of side effects after a while. So it doesn't exactly work like by doing "just" 70% everytime or in a long run, you need to take the whole package into the consideration and still, the recovery is the key and you only can do so much.