My take on the OPs original question was why can't HP represent just "meat", as opposed to any other meta explanation, such as luck, stamina, morale, skill, etc.
My answer would be that HP can't realistically be just meat as written because your 50 damage dragon bite would then have to have similar effects on both a level 1 and level 10 fighter at full health.
HP goes up as level (experience/training/skill) increases, yet meat (size/weight/thickness of skin) is not something I envision also increasing at that same rate.
Going just by the OP's statements, I don't think HP represents just pure physical damage (i.e. the number of times you can get stabbed in the heart without dying), but a person's ability to withstand/mitigate/roll with what would otherwise be debilitating/fatal blows (experience/training). In other words, your "been around the block a few times", which I find synonymous with lasting longer (fatigue), luck (more likely intuition and timing), skill (training and practice), and somewhat better muscle mass/endurance/ability to stay standing and fighting (stamina).
What differences did you have in mind when you say "experience" isn't meta, but these other non-meat factors are?