Pics of shower designs and real world are not always the same thing.

Yes shower floor requires slope. The smaller tile helps with grip so you don't fall.

Fairly standard request so be happy they know about slope and appropriate tile choice.

Every tile install needs cleaning. If that bothers you look for a prefabbed pan. Kohler makes a nice one that is cast iron like the old tubs. No creaks or hollow feel. No grout to worry about.

You'll have to take responsibility for the success of something he isn't experienced with. That means you have to find out everything required for a linear drain install with the size tile you want. Generally tile gets a rating for slipperiness when wet. I'd test out a sample to make sure you're safe using it. . . .If he isn't confident in doing the job contact a high end tile supply outlet for some recommendations. All this is work but you're the one living with it. Put the work in and get what you want. They don't make those drains because no one uses them. Here's a start-

Thats an old video/method with a infinity strainer not a bonded drain and an old thread on JB. theres more modern ways to go linear.

Truth is if you hired a skilled professional Tile contractor they would be happy to install large tile on the floor with any type drain, you dont need a linear drain perse'.

Upgrades come with upcharges and you may not have the skilled contractor for the upgrade

With the right contractor, and the right products, it's not an issue. Sounds like there is a question as to that contingent being satisfied though. You do want to have pretty grippy tiles do you don't fall and injure yourself. Textured tiles like that are a bit more difficult to clean. There are trade offs to all choices.

Take a look at this newer version of Infinity linear drain

If it is $1000 more, do you still want it? Might help to cut to the chase so you can make an informed decision.

With a center drain and a mud bowl, I have no problems going up to a 4" tile. Going larger than that and tile rocking and lippage can start to be an issue due ot the compound curves of a mud bowl. Depends on the size of the shower and shape of the bowl, the larger the shower the easier it is to get larger tiles to conform. That's my experience.

If you want larger tiles, with a center drain the installer can do a four-plane inverted pyramid shaped bowl. You'd have four triangular planes going from the shower wall to the drain, and you'll have tile cut lines going from the corners of the shower to the drain.

Or you can use a linear drain and use tiles as large as are practical. As you lose grout lines, you lose potential traction underfoot. So check the wet coefficient of friction of the tile you plan to use to make sure it won't be a slip hazard.

The only single piece stone slab shower pans I've fabricated myself have been out of soapstone.

The majority of the time I cut down larger tile to the size of the drain grate for a clean finish. This requires finishing all edges and $$$. This is a upcharge. Don't expect your tile setter to do this for the same price as 2x2's which is the norm.

Small tiles and a center drain are simple, standard and safe to stand on. If it were me, I'd go with that and spend the extra money on a nice Paul Klee print.

Im w/creative tile look how well thought out that last pic looks. Extra $$ = skill and thought or vision to see it and thats what makes it perfect.

Today people want cheap fast and pefect. As we see on hoooz daily its a myth. never happens. shop til you drop people