Does ChEMBL have a specific definition for what they mean with "Max phase for indication"?
This refers to the phase a compound has "achieved" in a clinical trial. 

Phases are typically ordered from 1 to 4 
(although phases 1-3 are most talked about, as they are needed to bring a drug to market):


  Phase 1: Testing of drug on healthy volunteers for dose-ranging
  
  Phase 2: Initial testing of drug on patients to assess efficacy and
  safety
  
  Phase 3: Testing of drug on patients to assess efficacy, effectiveness
  and safety (larger test group)
  
  Finally, there is Phase 4 (referred to in your example), which is
  after a drug has been approved (by e.g. the FDA or the EMEA): here,
  the effects of a drug while used on the general patient population are
  monitored.


See also https://en.wikipedia.org/wiki/Phases_of_clinical_research

Your example has been approved (i.e. it can be brought to market, or might already be available), while others might still be in ongoing clinical trials. Others might have been "killed" earlier due to e.g. toxicity or side effects. Or have not even entered clinical trials (which would be the majority of compounds). 

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