I've experience similar issues with older vSphere 6.x versions too. Some of the hosts apparently recognized the new datastore size, but some of them didn't, which resulted in an inconsistent datastore size in vCenter Server (and on some ESXi hosts), depending on the host which last reported the size to vCenter. Neither rescans from the vCenter UI, nor the ESXi UI helped. The only reliable way to work around this issue, was to run vmkfstools -V (please note the upper-case -V) on each host. Once done everything showed up as expected.
André