My basic understanding is that any mundane who can take the Poor Flaw or the Wealthy Virtue:
With the Poor Flaw, only has 1 season of free time/year.
With the Wealthy Virtue, has 3 seasons of free time/year.
But the description of the Landed Noble Virtue states that:
Poor Landed Nobles "must spend every season managing [their fiefs]". Ergo, zero free seasons/year.
Wealthy Landed Nobles "do not need to devote any time to looking after their lands". Ergo four free seasons/year.
Is this intentional or should it be erratad?
It probably should be erratad.
We have house ruled it that Wealthy and Poor work with Landed Noble as described bi the virtue and flaw, not as described within the Landed Noble virtue.
It may very well be intentional. A poor landed noble could easily be stuck half the year working the fields(or forest etc) himself, and the other half doing the administrative parts.
While a wealthy landed noble can easily afford to have minions do >99% of the actual work and basically sign a few papers after spending 20 minutes of hearing reports each week, or even month.
Of course, they can spend zero time with it and leave it all to their minions, but that is like begging for corruption troubles.
Go by individual case and if you smack down on the poor guy, give him some kind of compensation.