“No-format-at-all” does not exist in Writer. You always have some “format”, at least you have chosen font face and size which will determine line height. The font metrics may contain extra settings such as a systematic leading.
You also always have some paragraph style applied, be it Default Paragraph Style (but I strongly discourage its use because users, even advanced ones, don’t understand its role and the consequences of tweaking it). A paragraph style can specify spacing above and below.
Without any details about your “unformatted” page it is difficult to give a precise answer. Edit your question to attach a sample file. Mention OS name, LO version and save format.
When I write edit, I mean don’t use a comment but update/modify your question: click … under it, then the “pencil” icon.
EDIT: (after checking your sample)
I wouldn’t call your sample unformatted. You have a huge lot of direct formatting which disturbs the “common” layout which could be expected from a homogeneous paragraph (then using simple data from font metrics). Your direct formatting causes erratic line spacing. But in my Writer 7.6.6.3, Fedora 39, KDE Plasma desktop, the page is quite full (note that your font face is being substituted because it is not installed here).
I’d say everything is “nominal” considering the “perturbation” created by direct formatting.
