Should I be able to do it? I wanted to program MX-1200 to go to a hidden device page if I hold Page button for over 3 sec. Put an IF statement but it just doesn't work. As soon as I start holding the button, it just jumps to the next or previous page, before I even release it.

The same logic works fine with on-screen button. So perhaps Page buttons just have different behavior built-in?

I have a mx-450 and found the same thing. I wanted to have dual purpose hard buttons, i.e. make macros for the channel up and down with a 1 second delay, so I could use for the page up/down for my DVR, but no dice. The macro first step delay trick only works for the LCD buttons from what I can tell.
It sends the macro on the hard buttons after the original hard button command when a macro is assigned.

If you are saying you wanted the channel up and down buttons to react to quick button presses as a regular channel up and down function, but when pressed for a second to instead issue the commands for page up and down, then it is possible with a pc programmable remote with the Press and Hold Macro function.

I have an MX-980 and an MX-1200 working with an MSC-400 (I've got both remotes in my showroom system so I can compare the two). On the MX-980 I've programmed the MENU button in each activity with a Press & Hold macro. Tap the button for the Menu IR, Press & Hold >=2seconds for a jump to a SYSTEM SETTINGS page. This has always worked perfectly on the 980 but on the 1200 it just locks up the remote. It stops sending any commands and I have to remove the battery. I've even tried reversing the IF/ELSE command to be Press & Hold <1second for the Menu IR, ELSE Jump to SYSTEM SETTINGS page. Same result. I don't get it.