I don't understand this thing about different activities.
If I remember well the guy in the podcast is saying the passive skill is the floor in the case of a roll. That's applicable to the same activity or challenge. That's wrong according to the PHB.
He also says passive perception is always on, wrong again according to the PHB, because the passive check is there to substitute a dice roll, if the DM calls for dice rolls there shouldn't be any passive checks for the same thing at the same time so it can not be always on. It is clear:
"A passive check is a special kind of ability check that doesn't involve any dice rolls...can represent the average result...or....determine whether the characters succed at something without rolling dice."
"An ability check tests a character's or monster's innate talent and training to overcome a challenge. The DM calls for an ability check when the character or monster attempts an action (other than an attack) that has a chance of failure...If the total equals or exceeds the DC, the ability check is a success-the creature overcomes the challengeat hand. Otherwise, it's a failure,.."
There is nothing there about conscious or subsconscious activities, time or any other irrelevant metric, if there is a chance of failure to overcome a challenge there are 2 options, dice are rolled or a passive skill value is used. Not both. There is nothing there saying that you can ignore the roll and choose the passive value if your skill roll is lower than it. If we are talking about different actions and challenges it is the same thing, you apply one or the other for each one, consequently the passive skill can not be the floor for a dice roll.