Invalid variable names created by internalized rules

I stumbled across a case where a Rule# prefix is seemingly being appended to the beginning of a variable name for the generatedCounter cell possibly caused by using a claim as a lemma (the last request/response in this bug report). Is this a genuine bug? See https://github.com/runtimeverification/pyk/pull/959

<generatedCounter> in the response looks like this:

                  {
                     "tag":"App",
                     "name":"Lbl'-LT-'generatedCounter'-GT-'",
                     "sorts":[
                        
                     ],
                     "args":[
                        {
                           "tag":"EVar",
                           "name":"Rule#Var'QuesUnds'GENERATEDCOUNTER'Unds'CELL'Unds'6de8d71b",
                           "sort":{
                              "tag":"SortApp",
                              "name":"SortInt",
                              "args":[
                                 
                              ]
                           }
                        }
                     ]
                  }

Executing with the legacy backend yields the same variable name Var'QuesUnds'GENERATEDCOUNTER'Unds'CELL'Unds'6de8d71b without the Rule# prefix.