I have been all over Trane splits lately, and all the ones I look at have freeze protection on the coils. Almost every single one has required a leak repair that I have come across. These are less than 10 year old Trane splits. Also, I have changed quite a few txvs on them, the ones that thread on.
For upflow, the install manual tells you to remove that pan, and remove the horizontal baffle and replace with the narrow one. The narrow one is on top of baffle already screwed to the top of the coil. It reduces turbulence and such but if you leave it on, like hack said, if your unit is horizontal, doesnt make that much of a diff. i wouldnt think.
You can remove the horizontal pan and gain some efficiency, also the metal block off plate on top of the coil can be swapped with the supplied plate which is less restrictive.
Neither of those items will cause a coil to ice. More likely a refrigerant leak on the evaporator, with the paper thin tubes they are using, an then they rifle the inside for even less wall thickness. Dirty coil and or poor supply duct work are two common ones also.