Not quite.
Salary sacrifice leases have additional features, such as maternity protection, resignation protection etc, so that if an employee is off on maternity leave, to is fired, long term ill etc, then the employer is not left paying for a car, they can simply return it.
Some salary sacrifice scheme also insist on bundling tyres and maintenance/servicing as well, so that this burden is not left on the employer. Some go further and bundle the insurance too.
Finally you will see salary sacrifice schemes as having their wording / contracts approved by HMRC, if you do a business lease yourself and word your own sacrifice, you may be okay, but the employer loses some protection here if it is done wrong.
You will find the gross salary sacrifice lease costs are much more expensive than normal business leases for these reasons (I suspect they also build in a better profit margin too on salary sacrifice schemes TBH).