Yes it is possible to recharge/load/top-up these SIMs.

Why should one bother when the discounted street price of these SIMs in HK is much less than the cost of the reload.

Moondog, being very wise got a quantity discount.

Every frequent travellers to China have a few of these to pop in to their handset or MiFi for instant hotspot to access the world outside the GFW.
Since not all the VPN providers have 100% uptime, one need to have their bases covered when you must have that web conference at a specific time.

"Tricky rabbit has three escape plans" - my translation of Chinese proverb.