Wow! I admit, I tend to sink when I try to walk on water. And I also admit, I have never managed a network consisting of "10's of thousands" of nodes - that is certainly impressive! But I have managed many networks over the years consisting of hundreds of nodes, and many MANY more networks for SOHO environments, most with 50 nodes or less.
And to be sure, a SOHO environment is what we are dealing with here - not a monster "enterprise" size network that uses enterprise class routers.
Bullfeathers! It's not a roll of the dice!

Clearly Solaris is used to enterprise networks there typically are multiple network devices (multiple routers, multiple switches, etc.) and where IP assignments often come from a separate DHCP server or enterprise class router. That is NOT how it works on smaller SOHO environments where the DHCP server is running on the same home or small office router that manages the entire network.
Sorry Solaris, but that's more bullfeathers
for the OP's scenario. "Rotating mac addresses"? Come on!

You are talking BIG networks while the OP appears to have a small home network. Not once did he say anything about macbooks. Nor did he say he uses VMs - which again is typically within the realm of enterprise environment, or "some" advanced users. There is NOTHING to suggest any rotation of MAC addresses is going on here.
"Can cause issues?" Anything can cause issues, including static IP assignments, or conventional DHCP assignments.
Reservations work great in home and small office environments with networks of a single SOHO class router, PCs, laptops, printers, NAS, tablets and yes, even smart phones.
Sure it is. This is you thinking, once again, that SOHO networks are managed the same way as enterprise networks. NO! Today's SOHO routers allow
both DHCP Reservation and traditional DHCP assignments. That's what was being described there. It is also how I set up my own network and the many SOHO networks we are responsible for here.
For example, I would not set up a reserved IP for the computers or tablets. But for printers, NAS devices, security cameras, or the OP's aquarium controller, reserved IP addresses is a great solution.
This works because the odds two devices would have the same MAC address (which, in theory should never happen while in reality, it occasionally does) are very low, at worst.
I agree, it is not terrible advice. A mix of traditional DHCP IP assignments and DHCP reservations for SOHO networks a great solution. But there are times when static IP addresses may be a better solution too.
And no, they don't "always" cause problems - just as DHCP reservations, don't always cause problems either.
@Solaris17 - did you read the link I provided in Post #8 above (last line) in post?