Emerald today, 12/05/21, ~5:10pm central - server smells hot, ~175ms instead of the usual ~50ms for me (Nashville TN) - twice my Mag got stuck in boost mode - check it out. Made a vid and logged. Will also post in bugs.
This is true for all abilities when you're disconnected, you basically get that ability infinitely until your connection is re-established. This can happen during temporary spikes or complete disconnections. However you can only use that ability once, you can't toggle it or turn it on again in a disconnected state. For example the light assault can get infinite jetpack ability, but if I release the key while I'm still disconnected the ability will stop and not be able to activate again until I reconnect. Same concept for the magrider in your case.
I've been playing a lot in the past 2 months and I play a fair bit of magrider and haven't had it happen a single time so I imagine it's likely pretty rare these days.