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Yes, it seems they made quite a dent on Mars

I'm not so sure that this should be interpreted as "thrusters turning off prematurely" rather, it getting to the point of shut-off sooner (and faster) OR it stopped because they hit the ground

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That is when it switched from thrusters to lithobraking.

Lithobraking has actually been a feature in at least one Mars mission: the pair of impactor probes that piggybacked on NASA's unlucky Mars Polar Lander mission of 1999 [1]. The MPL itself, as is quite well known, ended up doing an unplanned lithobraking maneuver after its retrorockets shut down too soon (!) due to insufficient integration testing. The impactors were never heard of either; the exact failure mode remains unclear.

[1] https://en.wikipedia.org/wiki/Deep_Space_2

A proven method of matching planetary velocity.

I read in some of the reports (can't remember if official ESA, news, or twitter) that they were turned on for just 3 seconds (instead of the inteded ~50), plus the parachute was cut off earlier too. So, as this report from ESA says, it fell from at least a 1000 times higher than intended (the cut off altitude was 2m or so).

a 1000 times... that sounds rather metric.

It's an order of magnitude. 1e3, not 1.000e3 which would indeed be suspicious.

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