Those are a few separate claims:
I think people at quant companies use frontier models, sometimes spending thousands of dollars a month on tokens
Quants usually do not use deep learning to try and directly predict the market, though they might use it to process data. Even in 2018, everyone I knew in the field was quite excited about deep learning and reinforcement learning
Quants are generally open to rapid change, though they’re not likely to spend a lot of time on new tools until they’ve shown some clear benefit. The strategies you spent years working on can stop working overnight, and the market provides very strong incentives to adapt
(I work at a quant fund.)
Tell Claude Code to calculate some statistics without using for loops, and it will thrash around and often end up with for loops anyway. Tell it to write the code and then refactor it to remove for loops with vectorized operations, and it usually succeeds, and much faster.