It's only in 64-bit. I had that tagged, but I do not see any of my tags showing up in my post so I probably did something wrong. I take it you cannot reproduce this problem?
I created a VCL Forms application with a single button, and I can easily reproduce the problem in 64-bit (again, works fine in 32-bit). Here's a screen shot of XE7. Note if I hover my mouse over "Width" I get no tooltip, and you can see the error in the watch list. You will have to take my word the result in XE8 is the same (it's on a Mac and I cannot get it to do a screen shot).
Untitled.png
PS: I do get tooltips over the class itself (here Button1), and can then find the Width property that way. Or just assign it to a variable..