Yes the HPS ignitor is too weak, for the HQI it requires 3.5-4.5kV.  Of course the HPS ignitor will work sometimes, but not 100% of the time and especially not as the lamp ages.

In my experience, I have had an Osram HQI-T 250w/D metal halide lamp fire up and run reliably on a North American 250w S50 high pressure sodium CWA ballast without any problems using the original ignitor on the ballast.

In my experience, I have had an Osram HQI-T 250w/D metal halide lamp fire up and run reliably on a North American 250w S50 high pressure sodium CWA ballast without any problems using the original ignitor on the ballast.

But the point is, the pulse voltage should be sufficient even when components with their tolerances combined in the most adverse combination, include the most adverse operating conditions (mains voltage, ambient temperature,...) meet up. A single lamp in a one single fixture does not prove anything, except that it just /may sometimes/ work. Even when intentionally making the components on the edge of their tolerances (a common practice when testing a new design intended for mass manufacture) would require quite a few of them in the test group to give anything relevant in the test result.
Building a street installation this way will make half of the lanterns dark when the first winter arrives...

The M138 look like just the M153 (250W probe-MH), so for a 135V lamp, with an added ignitor.
The M80 is really build around the European 90V arc lamps (where the "HQI" came from), so 3A.
The difference is not only the output current, but the load characteristic as well:
The M80 is a HX autotransformer (with capacitor across the primary just for power factor correction), so the current decreasing with increasing lamp arc voltage (a feature coming from the series reactor and in fact required for thermal stability of many European lamps). It requires the mains voltage to be long time within +/-5% tolerance.

The M153 is (mostly) a constant current CWA, so the current remain quite tightly constant over quite wide arc voltage range. And the CWA means, it can tolerate quite some mains variations as well.

As far as I know, both North American 250W M138 and 250W M153 metal halide lamps are pulse start metal halide lamps that run at the same arc voltage drop (135V) and operating current (2.13A) as most 250W mercury vapor lamps in the world.