My understanding from other discussions is that the operating temp of the coolant is higher than 75F. The rate of passive heat dissipation via a heat sync is a function of the difference in temperature between the coolant and the air. If the operating temp is 90F* then they seem to be saying they need at least a 15F differential to dissipate the waste heat from the laser.
If you only have 10F differential, you can still run the laser, but the temperature would tend to rise to 95F or so before reaching equilibrium. Therefore, it would need to pause when the temp exceeds 90 and wait for it to cool to something lower before restarting.
*90F is a temp suggested in this post: Non-Pro Performance in warmer climates - #21 by PFI-Guy