A game with 5x30 sec byo-yomi could take quite a bit longer than the 25 minutes free time, so that's not a good comparison.

https://en.wikipedia.org/wiki/Byoyomi

After the 25 is up, each player can make as many moves in 30 seconds as they'd like, the 5 means that they can overstep that bound 5 times (by 30 second increments).