Like i've said your reply concerning Obito was meaningless since i never brought back the claim in OP and since i noticed it, i thought you didn't read the topic completely.
Concerning the sensing ability, it's perfectly understandable and i already explained how it works plenty of times
Sensors sense all the time as long as they kneed/concentrate chakra
You must be registered for see links
Now if they are too distracted, it can happen they fail to notice something they normally should have
You must be registered for see links
Reason why none of Hokages(sensors included) sensed a thing before Orochimaru told them about war:
You must be registered for see links
You must be registered for see links
Tobirama for example failed to notice Orochimaru's body was filled with his brother's cells before sensing it better(when Hashirama who was considered weak in sensing managed to):
You must be registered for see links
Tobirama also didn't notice Sarutobi's approach when he came to help Naruto:
You must be registered for see links
So really it doesn't depend on your level on sensing in this case but it depends on if the sensor in question is kneeding chakra to sense or not. Minato was capable to know Naruto managed to control Kyubi and that they were partner fighting together from a distance, just like he noticed it was extracted, so Minato is capable to notice chakra build up inside a body.
Sensing in Naruto is no particularly different than in DBZ. They sense all the time but there are times it happens that when they are too focused on something like in Minato's case, they fail to notice. Like Picollo failing to notice Cell's presence:
You must be registered for see links
Or Kurillin failing to notice Bejita behind him:
You must be registered for see links