No need to check if the first character is a number. This is already validated before.

scripts/o3de/o3de/engine_template.py

@@ -1894,6 +1894,10 @@ def create_gem(gem_path: str,
     # gem name is now the last component of the gem_path
     gem_name = os.path.basename(gem_path)
 
+    if not utils.validate_identifier(gem_name):
+        logger.error(f'Gem name must be fewer than 64 characters, contain only alphanumeric, "_" or "-" characters, and start with a letter.  {gem_name}')
+        return 1
+
     # gem name cannot be the same as a restricted platform name
     if gem_name in restricted_platforms:
         logger.error(f'Gem path cannot be a restricted name. {gem_name}')

scripts/o3de/o3de/utils.py

@@ -46,9 +46,6 @@ def sanitize_identifier_for_cpp(identifier: str) -> str:
         return ''
     
     sanitized_identifier = list(identifier)
-    if not (sanitized_identifier[0].isalpha() or sanitized_identifier[0] == '_'):
-        sanitized_identifier.insert(0, '_')
-    
     for index, character in enumerate(sanitized_identifier):
         if not (character.isalnum() or character == '_'):
             sanitized_identifier[index] = '_'