To explain the answer: the basic function of a thematic coefficient is to make a subset of the 10 possible moves highly salient, while putting some other (often larger) subset off the table straight away without having to think through any details of how their use would affect the "technical"/"procedural" aspects of the situation. In other words, it narrows the field of choice and the field of acceptable outcomes, making it easier to consider the options and settle on one.
Yeah, 1e certainly makes playing a magic user hard. I mean, the cognitively difficult part at low level is probably more figuring out "How can I make my 3 marginally useful spells (because that's all I randomly got in my book) do some useful work? Should I take 'Affect Normal Fires' or 'Mending' because I'm definitely taking 'Shield' as my first spell! How do I make my only 2nd level spell, 'Fools Gold' useful? Of course there is huge variation, if the DM let you capture some fat spellbook from a bad guy, then it is more a question of 'when do I unleash web?' and that's not so hard... So maybe 5e's 3rd level Wizard is a bit more involved, he's got more options DURING PLAY, but it could be easier to decide what spells to memorize.
I don't see how these two statements can sit side by side and cozily cohere.
Whether a cognitive workspace and attendant move-space is winnowed because of thematic salience or tactical/strategic salience is irrelevant to whether or not the actual play becomes more or less difficult to deploy skillfully in the course of playing a game in which (a) obstacles/conflicts exists and (b) they are meant to be overcome.
If a character in a game with thematic/premise-based heft has their cognitive workspace and movespace winnowed and they are therefore "easier to play skillfully", I don't see how it can also be said that a low level Wizard with an incredibly small subset of effective spells + 2 actual choices for loadout (who has massively decreased workspace and movespace) is somehow "more difficult to play skillfully" by writ of that winnowing.
I'm not saying I agree with either of those takes...but I don't see how they cohere.