The problem here IMO is that "reasonable use" is a loophole that can be used to justify anything, or at least it doesn't tell the customer how to use the device

The problem here IMO is that "reasonable use" is a loophole that can be used to justify anything, or at least it doesn't tell the customer how to use the device before expecting trouble. If the limitation was also expressed in objective, preferably quantitative terms, it would be clear. Internet conections usually have that: 1Tb transfer at 100Mb/s speed, then 64kb/s. 50% of the time, the speed may be limited by congestion, etc.