Suppose I write: {loSmaH wa' ben jIboghpu'} for "I am 41 years old".
Literally though, the klingon goes "41 years ago I have been born"
i.e. 41 years ago my "being born" has been completed.
Lets forget this for the moment..
If I write {wa'Hu' pItSa' vISoppu'}, this means that "one day ago my
eating the pizza has been completed". But I could have eaten this
pizza many days ago, and yesterday is just another day during which my
eating of the pizza continues to be completed.
So, can't the {loSmaH wa' ben jIboghpu'} be interpreted to mean, that
I am in fact older than 41, and that it is just that 41 years ago, my
birth (which took place way earlier) remains completed ?
So, why not write instead {loSmaH wa' ben jIbogh}, for "41 years ago I
am born", thus avoiding the ambiguity ?
You are interpreting Klingon -pu' as if it were English present perfect tense, which it is not.
English present perfect tense means that I'm talking about a time right now, and as of right now, the thing I'm talking about happened in the past. Happened in the past tells you when something happened; that means it's tense. Klingon doesn't have verb tenses.
Klingon -pu' means that, whenever an action happens, it is completed. The action is viewed as a complete unit, a whole that has no visible internal temporal flow. loSmaH ben jIboghpu'. Forty years ago, the action bogh occurred and was completed.
When you do not use perfective or continuous aspects, the verb is not perfective and not continuous. You're not just not mentioning whether it's those things; it's specifically not those things. loSmaH ben jIbogh means that you're in that moment of being born forty years ago. The bogh is not yet complete and not an ongoing action.
So no, you can't use loSmaH ben jIboghpu' to mean you're 42 or 50 or anything like that. -pu' doesn't mean sometime before the current time context; it means viewed as a completed whole.
Okrand says in The Klingon Dictionary that for consistency he will translate Klingon perfective into English present perfect tense, and then he only does it about half the time. We get lots of counterexamples, like yaS vImojpu' I became an officer (the becoming is done), De''e' vItlhapnISpu' I needed to get the INFORMATION (the need is over), vIneHpu' I wanted them (the wanting is over), qaja'pu' I told you (the telling is complete), Qaw''eghpu' he/she destroyed himself/herself (the destruction is complete). There are more.
So don't be fooled into thinking that -pu' is always translated by have/had/has verbed, or that it means exactly what those English phrases mean. English does not have verbal perfective; Klingon does. Klingon does not have perfect tenses; English does. They are not the same thing.
wa'Hu' pItSa' chab vISoppu' Yesterday I ate a pizza.
The eating happened yesterday, and it was completed.
-- SuStel http://trimboli.name