Had a conversation with a co-worker whos son in law shot a cull and had the head confiscated and fined entering California. Apparently they have a law stating that you cannot bring a deer head into the state containing brain matter. Unfortunately Texas law dictates that one must keep a bucks head entact. So in this situation one of the laws had to be broken to avoid paying a taxidermist to process the cull's skull and ship or getting a land owner statement.
This being said I know a multitude of Texas hunters cap thier buck skulls at the lease/ranch which I have been informed to be illegal.
From TPWD: http://www.tpwd.state.tx.us/regulations/fish_hunt/hunt/proof-sex/

Proof of Sex
Notice: It is unlawful to possess a deer, pronghorn antelope with proof of sex removed unless the deer or antelope is at a final destination and has been quartered. Proof of sex for deer is:

the head (skinned or unskinned) of a buck deer with antlers attached

Read the last paragraph on the page on your link:

EXCEPTION: Instead of proof of sex, the hunter may obtain a receipt from a taxidermist or a signed statement from the landowner or the landowner's agent containing the following information:

•Name of person who killed the wildlife resource;
•Date the wildlife resource was killed; and
•One of the following, as applicable: whether the deer was antlered or antlerless; the sex of the antelope; the sex of the turkey and whether a beard was attached; or the sex of the pheasant.

Read my post better. In thier situation landowner/agent wasn't available.
Plus I doubt many bother with landowner statement because they are ignorant to this law.