I think I know where the confusion lies.
The OP referenced a press release from DoF. It explicitly outlined 'key' employees. The topic ensued as to what is, what is not a 'key' employee. I proposed that the scheme be rolled out to all employees. That is, if an employer in a qualifying company, is experiencing high staff turnover on the factory floor due to, say, wage pressures in the economy, causing disruption in production and a tightening of cash flow. Being a qualifying SME start-up, it should be open to the employer to offer the terms of the KEEP scheme to its factory floor staff, rather than compete with more established competitors with greater cash resources, hampering the development of an otherwise good company with good products.
If the offer is beneficial to the employees (ie they already pay tax at marginal rate) they can, like the scientists and engineers etc, choose to avail of the offer or not.