It is not allowed by computer programs or by FIDE.
PGN is designed to be parsable by computer programs. Those computer programs depend on PGN files actually adhering to the specification. It would be similarly unambiguous if you numbered the ranks 9-16 instead of 1-8, but computer programs would not be able to read your game scores.
If you are not concerned about computers reading your moves and just want to save time writing on your scoresheet, you are still out of luck. The FIDE rules of chess say
C. FIDE recognises for its own tournaments and matches only one system of notation, the Algebraic System, and recommends the use of this uniform chess notation also for chess literature and periodicals. Scoresheets using a notation system other than algebraic may not be used as evidence in cases where normally the scoresheet of a player is used for that purpose. An arbiter who observes that a player is using a notation system other than the algebraic should warn the player of this requirement.
C.8 Each move of a piece is indicated by a) the abbreviation of the name of the piece in question and b) the square of arrival. There is no hyphen between a) and b). Examples: Be5, Nf3, Rd1.