I am listening to one of Sam Harris´ Daily Meditations. They invariably begin with something like this:
Ok, take any comfortable position, on a cushion, chair or coach
In principle, I like that. Below, in the first foto, that's who I am, by nature. The second foto shows what I do, even if I cannot perform in such perfection.
I am lazy. The thought of comfort reduces the resistance to beginning a meditation session.
But, is the "sit comfortably" instruction really best suited?
No, long-term it' s not for me, so I don´t do it. The more frequently I sit in the 7-points posture, the better it feels. Like a mountain, as they say...
My partner too prefers the cross-legged position. Not for scholastic reasons, but because it gives her a good grounded physical experience. Unfortunately, she has a knee problem that makes even a simplified version of this position painful. She rather skips meditation than using a less painful position. That's how much it is worth to her.
Why sit in a specific way?
The traditional literature has often somewhat strange explanations why the 7-point position is good for you.
The "Pointing Out the Great Way" (POW) method prescribes a specific way of sitting, as does Culadasa in "The Mind Illuminated".
POW refers to empirical research that shows why posture supports concentration. It's the even distribution and output of muscle

(Note: I could not find the quoted study, but I trust that it exists).
The Seven Point Posture
These are the traditional seven body points.
1. Feet- cross-legged
2. Spine– straight
3. Upper Trunk– upright and open
4. Hands– equipose
5. Neck– slightly bent
6. Tongue– touching upper palate
7. Eyes– half open, fixed, unfocused
You can refer to the detail through the attached links. I recommend Escoffier.
Resources
Akashige (1970)
Unfortunately I could not verify the given source via Google
Culadasa (Mind Illuminated)
Yates (Culadasa), J., & Immergut, M. (2017). The Mind Illuminated: A Complete Meditation Guide Integrating Buddhist Wisdom and Brain Science for Greater Mindfulness. Hay House Uk.
https://www.amazon.de/Mind-Illuminated-Meditation-Integrating-Mindfulness/dp/1781808201
Sam Harris (Website)
Sam Harris. (2022). Sam Harris. https://www.samharris.org/
Escoffier (7 Points)
Escoffier, N. (2022, June 25). Seated Like A Buddha : The Seven Points Posture Of Vairocana. Nicolas Escoffier, PhD. https://nicolasescoffier.com/seven-point-posture-vairocana/
Pointing out the Great Way (Retreat levels)
Pointing Out the Great Way - Retreat Levels. (2022). Pointing Out the Great Way (Original Foundation). https://www.pointingoutthegreatway.com/retreat-levels
Vairotsana (Seven-Point)
Vairotsana. (n.d.). Seven-point posture of Vairochana - Rigpa Wiki. Rigpa Wiki. https://www.rigpawiki.org/index.php?title=Seven-point_posture_of_Vairochana