I've been lucky enough to have experienced a couple 'good' prostate massages in my lifetime, not as many as I would have liked, and always on the 'prowl' for someone that knows how to do this.
One thing I had found was that if someone has short fingers, they're not going to be able to reach it! That is unless they stick their whole hand in there...
My ex had short fingers, and just couldn't reach it. And I have yet to find, or purchase a 'toy' on the market, that feels as good as a finger massaging it. (And I've tried a lot)
As far as 'forcing' an orgasm from just a prostate massage, I had never experienced that. Yes, that milking of pre-cum, but not a full blown orgasm. Though I had experienced orgasms by having dildos used on me. Was probably more of that combination of the penetration, possibly combined with the dildo hitting the prostate. But I still think more of the penetration aspect of it.
Sometimes depends how aggressive, intense or wild it gets too. Sometimes there is more stimulation in the back, which tends to overpower sensations in the front.
But for sure, a good prostate massage, although not taking a man to an actual orgasm, could still feel like one long intense orgasm 'to him'. At least from my experience.
Got to remember that a woman's orgasm can last for 'minutes', where that little 'high feeling' when a man cums only lasts for a few seconds, before it's all over and done with.
Again, from my experience, having a good prostate massage actually feels like I'm having a 'very long', (as long as the massage continues), intense orgasm, without actually cumming. A whole lot nicer than those few seconds...