Max heart rate is 188 bpm (see image below)
Based on %Max. HR the heart rate zones are applied (see image below).
Zone 5 calculation is wrong. It should be 169 bpm because zone 4 was 150 - 168 (see below image).
This is the correct behavior in Final Surge.
Can anyone confirm this on the device? It's a bug, and hopefully, the team can fix it.