Using Arithmetic in pipeline.yml Processor

Elastic Stack Beats
3

This kinda solves it:

  - convert:
      if: ctx.pac != null && ctx.pac.log != null && ctx.pac.log.tags != null && ctx.pac.log.tags.contains('MONITOR')
      field: pac.log.system.monitor.cpu.pct
      type: float

  - script:
      if: ctx.pac != null && ctx.pac.log != null && ctx.pac.log.tags != null && ctx.pac.log.tags.contains('MONITOR')
      description: formatting pct for dashboards
      lang: painless
      source: ctx.pac.log.system.monitor.cpu.pct = ctx.pac.log.system.monitor.cpu.pct / 100

But why do i have to convert the fields type with the 'convert' processor at all when i configured my field as 'float' within fields.yml?
If i don't i get a script_exception caused by a runtime_error because a type conversion exception because he assumes ctx.pac.log.system.monitor.cpu.pct is a 'String'. And i assume a cast for my field would do it also, but i would like not to use any of this because it's configured as 'float'.

Kind Regards