Quoting a Treasury Regulation issued in 2005 is something like quoting a Supreme Court decision issued in 1973. You should check on whether subsequent events have made it obsolete. In this case, the history is in Rev Proc 2017-33:

Section 1.179-5(c) was promulgated in 2005 and has not been amended to reflect the extensions of § 179(c)(2) to taxable years beginning before 2015. However, in 2008, the Treasury Department and the IRS issued Rev. Proc. 2008-54, 2008-2 C.B. 722. Section 7 of Rev. Proc. 2008-54 provides that for a taxable year beginning after 2007 and before the last year provided in § 179(c)(2) for revoking a § 179 election by a taxpayer for any § 179 property, the taxpayer will be permitted to make a § 179 election on an amended return for that taxable year without the Commissioner’s consent. Section 7 of Rev. Proc. 2008-54 further provides that until § 1.179-5(c) is amended to incorporate this guidance, taxpayers may rely on such guidance. Section 124(d) of the PATH Act amends § 179(c)(2) to make permanent the permission granted to a taxpayer to revoke a § 179 election for any § 179 property without the Commissioner’s consent. This amendment applies to taxable years beginning after 2014. As a result, some taxpayers are uncertain about whether a § 179 election for taxable years beginning after 2014 may be made on an amended Federal tax return without the Commissioner’s consent. Section 3.02 of this revenue procedure provides the rules for making such a § 179 election.