A bit confused here. The post you mention describes force closures happening when a node was offline, which makes sense if HTLCs were pending. Not sure why mempool fees are relevant here?
Force closes between (even professional) Lightning nodes happened every time mempool fees go through the roof.
Why?
#1 Lightning peers in a 2-2 multisig cannot agree on the recent mempool fee levels.
#2 LND by nostr:npub1jnpyfrfqlf0px47wcag5kukcluz9s6rxd92hkpq4n2wrxvyvnzjs65hegv and Core Lightning from nostr:npub1jg552aulj07skd6e7y2hu0vl5g8nl5jvfw8jhn6jpjk0vjd0waksvl6n8n can’t communicate properly
Agree, nostr:npub1e0z776cpe0gllgktjk54fuzv8pdfxmq6smsmh8xd7t8s7n474n9smk0txy, nostr:npub179e9tp4yqtqx4myp35283fz64gxuzmr6n3yxnktux5pnd5t03eps0elz4s, nostr:npub1axkh7zyats2ypljcqzclndswzs9rrxcz9zjsqtt0re40gmsxrz3swm58z7?
nostr:note1q76hcnmxtneyc6xje8vrwzgfmrg0wmy5aumcm5uxg3nxlnqa46cqsghsze
Discussion
But yes, the primary reason is an offline node.