That is weird although not the first time I've heard that happen. If you ask Dell they'll come out with some rubbish about the disks not being certified for that particular controller.
Dell has multiple market segments. There is "Enterprise" which is 512 or 4096 sector drives for their mainstream servers (PERC, etc.) controllers. There is "Enterprise Plus" which is normally 520 / 4112 or similar "oversize" sectors. I believe those are for EqualLogic and likely for EMC stuff these days. Then you have the low-end drives they sell in desktops / workstations. They don't qualify drives across segments.
Additionally, they don't qualify drives that were never sold on a system with that system. So if you want to use a modern 12gbps SAS drive in an older system, it isn't qualified / supported although it may work. Likewise for a 3gbps drive in a modern system. In general, you can go to the support page for a particular system and search the downloads for a drive model. If you find it, it is supported on that system.
Lets be honest it's just so they can charge a HUGE markup on the disks and force you to buy them. Here in the UK the Samsung branded 3.84TB PM1643 is £890 but Dell want £4679 for the same disk with a Dell label and some tweeked firmware (the tweek is probably just to block none dell disks).
They do it because they have customers who either don't care or are forced to purchase the whole system as a unit from a single supplier like Dell. The same thing is true with SFP / SFP+ optics from any manufacturer that tries to limit optics to only "approved" ones. The most egregious example has to be RAM in Cisco products. Dell realizes that some people don't want to pay extra and that's why they don't block non-Dell drives in controller firmware / drivers any more.
Most of the "special firmware" stuff is just tweaks to make things more compatible across multiple generations of Dell hardware. As an example, some newer drives sold in systems with PERC H700 controllers report that they are SPC-3 compliant, not SPC-4, because if you issue a SPC-4 command to a drive via H700 passthru, the H700 will get quite unhappy and hand out errors. That's also the reason that some drives that are 12gbps in their generic version are only 6gbps in their Dell variant.
Dell doesn't have the source code for drive firmware and doesn't want to install firmware to convert generic drives even if they did - they get the drive manufacturer to load the firmware and put a Dell label on the drive. And if Dell (or HP, IBM, whoever) found a serious bug in drive firmware and reported it to the drive manufacturer, you'd see the fix show up in the generic firmware as well if it was generally applicable. Note that this doesn't necessarily mean that the drive manufacturer will make fixed firmware available to purchasers of older generic drives, just that new drives will ship with the fixes. See the next paragraph.
One thing I like about Dell-branded drives is that there are firmware updates available - all too often with the generic drives it is a huge PITA (if even possible) to get firmware updates for existing drives. With Dell, you just go to their support site and download whatever the latest version is.