Advantages and disadvantages in working after PhD while waiting for postdoc
Work in a research position rarely starts or stops cleanly at a particular time: in addition to the work one is doing right now, there are proposals to develop for the future and the ghosts of projects past to write up and work their way through the publications pipeline.

When you move around between research-linked positions, whether in academia or industry, this is generally understood, and there is at least some space to keep these subsidiary aspects of a research career in motion.

If you step out into the "normal" working world, however, this is likely to not be the case.  This is doubly so in a high-intensity job, like being a quant, where you are likely to be asked to work quite a bit of overtime.  Thus, the impact of taking a non-academic job is likely to extend well beyond the apparent time that you work it, as you find yourself forced to abandon opportunities that you might have been able to pursue in a job more closely connected to the research world, putting a "bubble" into your career that will take time to work out even after you rejoin the research world.

That's not to say it's the wrong choice---your preferences and circumstances may well make it a better choice---but it's important to understand this is an important reason why what are intended to be temporary periods outside of the academic/research world have a tendency to become permanent.