I think this is a bit of a moot point tbh, even if you couldn't do it with scouts you could do it with other troops. Granted, you could see the attacks coming and therefore they would be easier to dodge, but with a bit of data analysis and careful thought it would be still be possible to estimate enemy send times to within a few seconds. Therefore using precisely timed single unit "scoutings" as a method to determine hero position would remain perfectly usable as a defence tactic. Likewise, it is and always has been avoidable, as emphasised in earlier comments.
with troops you can react a properly as you see attacks incoming make a different time send with out hero. With scouts you only see that after you send your attack. So you have to hope that they failed to catch you or cancel. If you cancel you show that other attacks are fakes. So it's lose lose situation.
Like one comment said: it's no risk and really high reward method. So basically new kingdoms can't win if they are same size vs a kingdom of old players. "One plays with close cards other plays with open".