Has anyone been told this by a reservations CM because I get a different story....
Different WDW reservations CMs have recently told me that theme park view rooms will have an unobstructed view of the castle...I was recently told this for rooms booked at the Grand Floridian, the same as I was told for the Polynesian... and they said that some rooms with a blocked view (usually a tree) are lagoon view rooms. So, an angled view of the castle maybe... but not NO view of the castle... and I'll assume that if I have to put my self in danger by leaning over the balcony to see the castle... that's not a theme park view room.
I can't imagine anyone paying about $500-700 more a week to look at space mountain.
I've never asked about the views and also most of my "theme park views" were in the days before the category even existed (used to be only Lagoon or Garden, plus concierge levels and suites) - lately we either stay club level or garden view. Anyway, not sure about the unobstructed view of the Castle. If you can see Space Mtn, odds are you'd be able to see Cinderella's Castle as well.
I think a LOT of people complain about the views and that is why Disney keeps tinkering with the names of the categories (most recently in the case of the Polynesian). I'm actually glad that for the Royal Palm Club level they have finally put Theme Park View rooms in their own category - just so that people can be SURE of what they're getting. However, the prices are

For example, for $810/nt during regular season, you can have a standard room in the main bldg. without a view of the Castle and for $855 WITH the Castle view. Non-club level, TPV rooms are $615 during this time period (these are rack rate, weekend night prices). It's getting pretty crazy!
My only experience with what constitutes a "TPV" at GF is that about two years ago, I booked a GV room at the GF. A day or two before I arrived, I checked my on-line reservation and saw that my room category had changed to "Theme Park View" or "Magic Kingdom View" or whatever they were calling it at that time

. I had been magically upgraded and was really, really thrilled. Our room was in Big Pine Key and was a corner room with two balconies and a good bit of extra space. Views from within the room were of the lagoon on both sides (our room was in the lower right corner of Big Pine Key in the image below, from allears
From one balcony, we could see Wishes every night

This was our view by day:
Looking ahead from this same balcony:
Looking to the right of this same balcony (had I been standing up, you would be able to see the lagoon and peeks of the Poly)
Hmmm.. interesting what the cast member said about the Castle View. I can understand that rooms with partially blocked views are "lagoon views" - that is how it is over at the Poly too. I guess I just always assumed that "theme park view" meant a view of the theme park, not the castle.
If Disney means Castle view, they should call it that! 
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I totally agree!