Hmmm yes and no. If I set / to mount read-only in some embedded Linux system context, my intention is just that the contents of disk shouldn't change just because some program decided to write something somewhere; I would be quite surprised if some recoverable metadata bit flip or something caused the system to irrecoverably fail to boot just because the readonly flag also prevented fsck from fixing errors.

However if I have a faulty drive that I connect to my system to recover data from it and I don't want it to experience any more writes because I'm worried further writes may break it further, I would be quite surprised if 'mount -o ro' caused the driver to write to it.