For the effort you are expending, just getting a hard drive makes way more sense even if the $/gb is technically a little worse. The utility of hard drives is much better.
In terms of external tampering, I think that need is better-served by encrypting everything, which you probably want to do anyway. Or at least using some sort of checksum signed by a key.
However if the focus is "what if the backup process is compromised", then yes, having some date which is beyond its writing-reach may be useful. Another aspect of this might be a remote-backup system where one set of credential is enough for daily backups and restore, while another is needed in order to access a set of older duplicates that are remotely maintained as ransomware-protection.
Do they break in from the ventilation shafts overhead?
I mostly agree, but the 25GB M-Disc EOL media format is fairly interesting for archival purposes. The gamble actually made sense in this rare instance as each active project folder still fit on one disc, and the $120USD omnidrive firmware drives should keep the retro-equipment running for a few more years. These are relatively inexpensive even with a spare unit in the box.
>just getting a hard drive makes way more sense
In many cases this can be true, but the 3 years of HDD flight time compared to the 7+ year SSD wear life is also fairly close. It is weird, but the cost of higher capacity 18TB/24TB HDD also no longer make sense for JBOD either... unless you are hitting rack space constraints. =3