The pre-game is an *optional* tool for a GM and player to get together and work up a viable background for a character. People in realistic societies are restricted in their choices by family, law, societal approval, friends, education, social status, etc.
If you are referring to the pyrokinetic serf girl in one of the pregame examples I've seen online, those are all realistic choices the player was presented with. How many choices did you have at 14? 15? 16? 17? 18? You would have even less if you were a female serf living in poverty with little to no education and bound to the land with no hope of ever (legally) leaving. Your default options are to get married young, pop out some babies and live the rest of your life working the land with your family, never seeing much past the area you were born in. Now, if you want to change that destiny, a whole bunch of problems present themselves rather quickly. You can probably never earn enough money to buy your freedom. Your family and friends will call you crazy and tell you to settle down and be realistic about your options. The lord will caution you against running away or will send armed men after you to drag you back and be whipped and humiliated in front of everyone you know, plus your family will be fined 100 pence, which is a fortune for a serf, like most of their yearly income, so you must think of the hardship your actions will have on your family (who will be fined whether you are caught or not). Your best chances are to run away, or petition to join a nunnery (which the lord may approve to garner good will with the church). Harn's default setting is sexist, as historical earth was at the time, but of course that is easily changed if you wish it. Anyway, I'm trying to point out that the pregame scenario was realistic. A character of a higher social class (not a slave or serf) would have many more options available.
Keep in mind the pregame starts out around 14 and stops when you get to 18 or finish your training in your occupation. It generates friends, family and geographical data for a character so they have a real feeling for where they come from and who they are, and why they are the way they are. I think it is a valuable tool.
Characters--and this is a major problem I have with D&D--do not spring forth from whole cloth as born adventurers, yet the D&D rules basically assume this to be the case and offer little background aid. Harn generates everything for you by choice or random die rolls as your GM prefers, in or out of a pregame; in fact, generating a character's background and family are all required and done before anything else, they are deemed so important.
The pregame is not even in the HarnMaster rules except as a brief blurb in HM 1e. I don't think it appears at all in HM Core (2e). Every pregame is therefore different, as each GM will gave a different way of doing it. And again, it is merely an optional tool to help players fit into the game world in a realistic manner. This can be done without a pregame, of course, and will work fine that way as well, so long as the GM (and possibly player) are willing to do the work ahead of time to flesh out the PC's past history.
HarnMaster is about individuals, not cookie cutter archetypes, though you can play them if you wish... why you would want to (and this conformity is stressed in every edition of D&D, though much less so in 3e) is beyond me, but to each their own. HarnMaster has no classes, no levels and if you want to do something, you tell the GM, he thinks about it, consults the rules for advice perhaps, and then makes a ruling on the fly as to whether it is possible or not. Things are much less set in stone in HM, giving the GM complete creative control without being castrated by rules lawyers, munchkins and power gamers questioning his every move. So players and GMs are both free to try new and unexpected ways to do things.
Imagine a player saying, I want my PC to use this psionic power against this target. And the GM asks, "What effect are you trying to achieve?" The player suddenly realizes he has more than one option (even options not covered in the rules) and maybe should think up something new and creative rather than use what he thought was the only way he could do something. The Charm psionic talent in the rules allows you to overload a target's senses, "freezing" them in place, but I've houseruled that it can be used to subtly influence the target to regard you more favorably instead (by providing a bonus to Communication skills against that target). If a player had another idea that sounded reasonable, I'd be happy to come up with a ruling on the spot, favoring fun more than anything. The HM rules enccourage this and provide extra options and advice in sidebars to assist with expanding the game in any direction you choose.