The behavior is actively endorsed by the platform.

Back in my day, we had this feature on Windows Vista called ReadyBoost that took advantage of the low-latency of flash media to supplement our slow HDDs. I’m not sure if there was a direct replacement for this in the Linux world. There are filesystems that take advantage of faster tiers of storage, but different latency tier exploitation isn’t something that I know to be readily available.

Today, 2GB of USB flash is next to useless, but I would consider a homebrew rescue system to restore your backups and fix problems without needing to prepare an external flash drive.