I think you're being a little uncharitable to people who promote interventions that seem positional (e.g. greater educational attainment). It may be true that college degrees are purely for signalling and hence positional goods, but:

(a) it improves aggregate welfare for people to be able to send costly signals, so we shouldn't just get rid of college degrees;

(b) if an intervention improves college graduation rate, it (hopefully) is not doing this by handing out free diplomas, but rather by effecting some change in the subjects that makes them more capable of sending the costly signal of graduating from college, which is an absolute improvement.

Similarly, while height increase has no plausible mechanism for improving absolute wellbeing, some mechanisms for improving absolute wellbeing are measured using height as a proxy (most prominently nutritional status in developing countries).

It should definitely be a warning sign if an intervention seems only to promote a positional good, but it's more complex than it seems to determine what's actually positional.