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Yes, correct, the ram was not primarily used as a boarding device. But other boarding devices did exist that were primarily used for that purpose well before the First Punic War.

Polybius speaks up the beauty of the corvus, it plays a major role in a couple of battles, and then disappears very quickly, it's a bit of an enigma. Though we need to keep in mind that Polybius wasn't even born until 67 years or so after the First Punic War started, and not in Rome until about 95 years after. There's zero expectation that he's going to know the exact actions occurring during each naval battle (and this is the case for most naval battles in antiquity), but he can create a really good narrative. His objective is, after all, to talk about how Rome became the greatest power. He states this outright in his work so it's not exactly some hidden bias.

He also creates this dichotomy of where Rome is apparently only entering the sea for the first time at the start of this war, but also reportedly had naval treaties with Carthage dating back to the start of the Republic. As it is written, it doesn't make much sense. Perhaps he's speaking of Rome as more of a unified state, perhaps, but this story does match similarly to what other Greek historians did with navies (Herodotus and Athens for example). We definitely know there's more going on there though, and from the 70s onward we really start to question Polybius on this. But it wouldn't really be until with Steinby throwing down the gauntlet to challenge historians in 2007, and it picking up steam from about 2017 onwards with Harris and others that we started to really try and figure out what was going on if not what Polybius was describing. Projects like the Egadi's Island project and studies on iconography have helped to slowly morph our understanding but there's still a lot of unknowns; the evidence for this era was just not great. I know there's a few projects in the works at the moment that should hopefully make things a bit more clear though, but cannot comment too much as they are still unpublished.

As for the corvus: Campbell argues it was a grappling hook (he wasn't the first but he's the only one that comes to mind right now), and de Souza and others have discussed how similar hooks were called corvii in later Roman works but long after. I do think Lazenby is correct to say we need to be careful with these later named tools, but there's still plenty of reason to question whether it was a grappling hook in these earlier instances as we know they are using these in Sicily and obvious Sicily has a large impact on seafaring in the region. Polybius described some other siege weaponry almost exactly like he described the corvus later in his work, this may show where some of the inspiration for how he imagined the corvus came from.

This is not to say that we need to bin Polybius, again there's not a lot of evidence from the period and Polybius is incredibly important to our understanding of this period. But we do need to be a bit careful and not take everything he says as gospel. As stated before, Wallinga's work on the corvus and investigating Polybius from a scientific standpoint was a good step forward as well, but the era was still dominated by traditionalists and for the longest time Polybius was gospel.

Writing this quickly on my phone so hopefully not too chaotic, excuse any errors.