Wow, thank you for saying exactly this, this "deferred anxiety" probably does partly explain sleep issues I've had the last 3-4 years. I agreed with GP's comment and have more issues with screens, but didn't even notice this difference in how I take my walks now.

Sometimes my inner thoughts can crowd aside the podcast and I'll get home and realize I didn't hear anything from the podcast, but more often it keeps me distracted the whole time. I think unplugging from podcasts on walks and in the car is definitely worth a try.

Walking and movement is supposed to be a massive help for sleep, but in periods where I have more anxiety, this effect is stronger than the benefits of the walk itself. I manage a quite decent hygiene around my phone use, but buying in-ear headphones was quite a mistake on my part, as I found this difference quite soon after.

at least according to "irresistible" by adam alter, it's also close to the definition of behavioral addiction, more broadly when we routinely maladapt to engage with a certain behavior to avoid emotionally uncomfortable that gets worse due to the avoidance.