fwiw I can certainly see the OP's pov as I tenaciously resisted changing my Ambit256 for years because normal CS agents were futilely trying to inflate my package with offering a SH1 and additional subscription.
My 10mbps tier on SACM was quite adequate for my usage profile.
It was only when I was in the middle of a lengthy 5 month SNR/FEC issue in Sept 2012 that having contacted Retentions for monthly "partial loss of service" compensation that they reviewed my whole package and offered a SH1 (with 30/2Tier upgrade) + VHD STB at
LESS than I was previously paying (no install/admin charges either)!
So it can be done but presumably depends on who you speak to in Retentions, length of service, duration/type of any existing fault, bundle type etc...
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Rgds - TW
20+yrs customer currently on Vivid 200/20Mbps service tier via SH3(VMDG505) hardware:v10 firm/software: v9.1.1912.304 and/or <cough> others,

provisioned from brig19 Arris E6k (BN3 7Nx node).