Scout Ships...

The scout has no drives, the colony ship does.  It does get a speed boost by virtue of being tiny, +2 I think?

I agree with the op in that it is counterintuitive for the tiny searcher ship to be slower than the medium-hulled surveyor and the cargo hulled colony ship.

It feels wrong.  Not arguing realism.  Fully understand that larger ships would have vastly more speed in space than smaller ones from any conventional physics standpoint.

Too much realism can quickly kill a good game, too little kills immersion.  In my opinion Gal Civ 3 has erred on the side of too little.

Back to the Op:

I don't think so.

It has a base move of 2 modified by +1 due to your race's "Fast" trait.

If you create a race with "Dense" your tiny hull should have enough capacity (30) to have an engine on the default template.  I don't know if it will, I've never tried it and I do not know how the module priorities in the .xml for that core design are layered.  I do know that it's viewable and that a modder, I am not, could post it here with ease.

Solution:  Mod the starting scout ship to be the small-hulled scout instead of the tiny one- or petition the devs to make that change to the game.  The mod would have to be entered separately for each race ,I believe.

There's another option that would fix your immersion quandary suggested here: https://forums.galciv3.com/474028/page/2/#3615447  (modifying the base stats of ships based on hull size and ship role, like ManiNames "thinks?" )

No. All ship hulls have a base strategic movement of 1 action per turn, unless you're playing with a mod that changes that. The starting scout should have a hyperdrive component, which gets you to 2 actions per turn, and the third action per turn comes from the empire bonus Fast 1.

The starting ships work off StaticShipBlueprintDefs rather than ShipBlueprintDefs; increasing the hull capacity of the faction won't result in having better starting ships because the starting ships don't have any filler components assigned.

As far as the module priorities goes, it's quite simple. The blueprint files are a list of the components which get added to the design, with the components listed first being added first. Components listed in <RequiredComponentType> and <ComponentType> entries are only added once per entry; components listed in <FillerComponentType> entries will be added in the order in which the <FillerComponentType> entries appear until no more will fit on the hull, looping through the list of filler components as many times as is required to fill the hull to capacity. All components listed in <RequiredComponentType> entries must be available and fit the hull in order for the design to be available for construction, while components in <ComponentType> and <FillerComponentType> entries do not need to be available or fit the hull before the design becomes available for construction and early entries will be skipped over if the components requested will not fit while the components requested by later entries will - though note that an entry will be skipped only if the component requested by that entry will not fit in the available capacity remaining at the time the game reaches that point in the component list; the game will not look at the list and say "gee, the design already has 30 range, maybe we should skip these three life support components in favor of the hyperdrive further down the list" or anything like that.