I’ve experienced this issue firsthand, although it’s more like 3 to 4 seconds. Changing the user agent to Chrome causes videos to load instantly, and restoring it to the original user agent causes the “lag”.
Some possibly relevant information: I’m running Firefox with unlock Origin on Linux Mint. I’ve also received the “playback will be disabled after 3 videos” message in the past – so it’s possibly only affecting users they strongly suspect are still using ad-blockers with workarounds.