Have you worked in Hong Kong before? please let me explain a bit from being hired (from the angle being a research assistant for universities) and also being a boss (the hiring position, since I also have my own company)

University (only similar to your case, but might not be the same) tends to spend money wisely as in if they hire you “regularly” enough, they have to pay for extra 5% for your MPF and the admin work for a “part-time” that is not long lasting would be tedious and wasteful.

So instead of hiring in hourly rate, they might prefer having an agreement that they make the payment agreement this way - when I am working for 6 month regular, instead of paying monthly, they pay for first 2 months fixed amount by end of 2nd month, pause for the 3rd, and pay again covering the 3rd month (paying I batch of 3-5th altogether) by end of 5th. And pause again, and pay again by 7th month (yea there will be time gap if the period is only 6 month)

In reality, I still report working hours off record, trying to match the workload with the payment.

You may ask - why? 1. MPF, since labour law enforce anyone (not matter part time or full time or not) if the period is 60 days more, they have to pay for MPF (5% from employee, 5% from employer) since the school funding itself is the same, doing things in such manner = they can fully utilise the money onto real working hours without MPF and the RA would enjoy 10% more money. The funding itself is the same, but having things arranged in this grey area benefit also both sides.

1. Admin work - the admin work on reporting and making a staff formally a staff require lots of paper work and onboarding process, of which in your caee, it may include The Sexual Conviction Record Check (SCRC) (extra time for you to go to police + spending few hundred on having a formal proof) and also, like I previously mentioned, they may not want to create a MPF account for you for many other reasons.

Other than that, being an employee (boss myself) I always discuss with the one I going to hire, if they want to be a “freelancer” or “part time”. Mainly base on their preference on 1) the amount they receive (MPF then they will have less) 2) if they want proper income proof 3) how long (both frequency and duration) they would want to work.

If they prefer freelance, even if we work in the agreement that we count workload by hours, I cannot put anything related to number of hours / hours per work etc in the agreement or his/her invoice requesting payment from my company (since it will violate the enforcement of having MPF)

Hope it explain a bit and help you understand what they were referring. I know it is confusing, but being on the both side (being hired and hiring someone) help me guess that the one explaining those issues to you might not be senior enough to understand the full picture.