What is this based on @Looney Toons ? I searched specifically for figures referencing "yards" and the only result referring to total wall being built in hundreds of yards was a CNN article that is not about the total length of wall (it's a few hundred yards out of a two mile section).
BBC from late 2020 claims 15 miles of totally new protection, plus 350 miles replacing or reinforcing existing. ABC doesn't dispute a hundred miles were built by the start of 2020. The New Yorker also states "three hundred and fifty miles" were constructed in 2020. None of these could remotely be called pro-Trump sources, yet they don't dispute the numbers were in the hundreds of miles.