Of course you can increase it from day one, in fact you had better or else you're not actually learning.
What you probably heard was that everybody is built with a natural maximum level of force they are able to generate with their body. A ceiling. Once you've polished everything and are doing everything right, you're not going to be able to improve that power even more. Kinda like you can only get so healthy or run so fast. Some people have more some have less, but everyone can improve what unpolished ability they have with training their technique.
The good news is, for 98% of people, that ceiling is unbelievably high. For the top 10-20% of those 98%, it's even higher than that.
If Woody Allen had done everything he could to be his best, he could most likely generate some scary force, more than enough to deal with most tough guys, and nobody calls that guy gifted.